[v5,1/1] dmaengine: switchtec-dma: Introduce Switchtec DMA engine PCI driver

Commit Message

Kelvin Cao May 18, 2023, 4:59 p.m. UTC

Some Switchtec Switches can expose DMA engines via extra PCI functions
on the upstream ports. At most one such function can be supported on
each upstream port. Each function can have one or more DMA channels.

Implement core PCI driver skeleton and DMA engine callbacks.

Signed-off-by: Kelvin Cao <[e-mail]>
Co-developed-by: George Ge <[e-mail]>
Signed-off-by: George Ge <[e-mail]>
---
 MAINTAINERS                 |    6 +
 drivers/dma/Kconfig         |    9 +
 drivers/dma/Makefile        |    1 +
 drivers/dma/switchtec_dma.c | 1570 +++++++++++++++++++++++++++++++++++
 4 files changed, 1586 insertions(+)
 create mode 100644 drivers/dma/switchtec_dma.c

Comments

Christoph Hellwig May 19, 2023, 3:56 a.m. UTC | #1

> +/*
> + * Use vender/device and class to identify the DMA function.
> + */
> +#define SWITCHTEC_DMA_DEVICE(device_id) \

I'd word this as:

/*
 * Also use the class code to identify the devices, as some of the
 * device IDs are also used for other devices with other classes by
 * Microsemi.
 */

to emphasis on why this macro even exists.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Vinod Koul May 19, 2023, 11:22 a.m. UTC | #2

On 18-05-23, 09:59, Kelvin Cao wrote:
> Some Switchtec Switches can expose DMA engines via extra PCI functions
> on the upstream ports. At most one such function can be supported on
> each upstream port. Each function can have one or more DMA channels.
> 
> Implement core PCI driver skeleton and DMA engine callbacks.
> 
> Signed-off-by: Kelvin Cao <[e-mail]>
> Co-developed-by: George Ge <[e-mail]>
> Signed-off-by: George Ge <[e-mail]>
> ---
>  MAINTAINERS                 |    6 +
>  drivers/dma/Kconfig         |    9 +
>  drivers/dma/Makefile        |    1 +
>  drivers/dma/switchtec_dma.c | 1570 +++++++++++++++++++++++++++++++++++
>  4 files changed, 1586 insertions(+)
>  create mode 100644 drivers/dma/switchtec_dma.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e0ad886d3163..24e8d4463592 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -20346,6 +20346,12 @@ S:	Supported
>  F:	include/net/switchdev.h
>  F:	net/switchdev/
>  
> +SWITCHTEC DMA DRIVER
> +M:	Kelvin Cao <[e-mail]>
> +L:	[e-mail]
> +S:	Maintained
> +F:	drivers/dma/switchtec_dma.c
> +
>  SY8106A REGULATOR DRIVER
>  M:	Icenowy Zheng <[e-mail]>
>  S:	Maintained
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index f5f422f9b850..cfc8b1988a3b 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -610,6 +610,15 @@ config SPRD_DMA
>  	help
>  	  Enable support for the on-chip DMA controller on Spreadtrum platform.
>  
> +config SWITCHTEC_DMA
> +	tristate "Switchtec PSX/PFX Switch DMA Engine Support"
> +	depends on PCI
> +	select DMA_ENGINE
> +	help
> +	  Some Switchtec PSX/PFX PCIe Switches support additional DMA engines.
> +	  These are exposed via an extra function on the switch's upstream
> +	  port.
> +
>  config TXX9_DMAC
>  	tristate "Toshiba TXx9 SoC DMA support"
>  	depends on MACH_TX49XX
> diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
> index a4fd1ce29510..977c97cda53d 100644
> --- a/drivers/dma/Makefile
> +++ b/drivers/dma/Makefile
> @@ -70,6 +70,7 @@ obj-$(CONFIG_STM32_DMA) += stm32-dma.o
>  obj-$(CONFIG_STM32_DMAMUX) += stm32-dmamux.o
>  obj-$(CONFIG_STM32_MDMA) += stm32-mdma.o
>  obj-$(CONFIG_SPRD_DMA) += sprd-dma.o
> +obj-$(CONFIG_SWITCHTEC_DMA) += switchtec_dma.o
>  obj-$(CONFIG_TXX9_DMAC) += txx9dmac.o
>  obj-$(CONFIG_TEGRA186_GPC_DMA) += tegra186-gpc-dma.o
>  obj-$(CONFIG_TEGRA20_APB_DMA) += tegra20-apb-dma.o
> diff --git a/drivers/dma/switchtec_dma.c b/drivers/dma/switchtec_dma.c
> new file mode 100644
> index 000000000000..2df6ad5c3ce6
> --- /dev/null
> +++ b/drivers/dma/switchtec_dma.c
> @@ -0,0 +1,1570 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Microchip Switchtec(tm) DMA Controller Driver
> + * Copyright (c) 2023, Kelvin Cao <[e-mail]>
> + * Copyright (c) 2023, Microchip Corporation
> + */
> +
> +#include <linux/circ_buf.h>
> +#include <linux/dmaengine.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/delay.h>
> +
> +#include "dmaengine.h"
> +
> +MODULE_DESCRIPTION("Switchtec PCIe Switch DMA Engine");
> +MODULE_VERSION("0.1");
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Kelvin Cao");
> +
> +#define	SWITCHTEC_DMAC_CHAN_CTRL_OFFSET		0x1000
> +#define	SWITCHTEC_DMAC_CHAN_CFG_STS_OFFSET	0x160000
> +
> +#define SWITCHTEC_DMA_CHAN_HW_REGS_SIZE		0x1000
> +#define SWITCHTEC_DMA_CHAN_FW_REGS_SIZE		0x80
> +
> +#define SWITCHTEC_REG_CAP		0x80
> +#define SWITCHTEC_REG_CHAN_CNT		0x84
> +#define SWITCHTEC_REG_TAG_LIMIT		0x90
> +#define SWITCHTEC_REG_CHAN_STS_VEC	0x94
> +#define SWITCHTEC_REG_SE_BUF_CNT	0x98
> +#define SWITCHTEC_REG_SE_BUF_BASE	0x9a
> +
> +#define SWITCHTEC_DESC_MAX_SIZE		0x100000
> +
> +#define SWITCHTEC_CHAN_CTRL_PAUSE	BIT(0)
> +#define SWITCHTEC_CHAN_CTRL_HALT	BIT(1)
> +#define SWITCHTEC_CHAN_CTRL_RESET	BIT(2)
> +#define SWITCHTEC_CHAN_CTRL_ERR_PAUSE	BIT(3)
> +
> +#define SWITCHTEC_CHAN_STS_PAUSED	BIT(9)
> +#define SWITCHTEC_CHAN_STS_HALTED	BIT(10)
> +#define SWITCHTEC_CHAN_STS_PAUSED_MASK	GENMASK(29, 13)
> +
> +static const char * const channel_status_str[] = {
> +	[13] = "received a VDM with length error status",
> +	[14] = "received a VDM or Cpl with Unsupported Request error status",
> +	[15] = "received a VDM or Cpl with Completion Abort error status",
> +	[16] = "received a VDM with ECRC error status",
> +	[17] = "received a VDM with EP error status",
> +	[18] = "received a VDM with Reserved Cpl error status",
> +	[19] = "received only part of split SE CplD",
> +	[20] = "the ISP_DMAC detected a Completion Time Out",
> +	[21] = "received a Cpl with Unsupported Request status",
> +	[22] = "received a Cpl with Completion Abort status",
> +	[23] = "received a Cpl with a reserved status",
> +	[24] = "received a TLP with ECRC error status in its metadata",
> +	[25] = "received a TLP with the EP bit set in the header",
> +	[26] = "the ISP_DMAC tried to process a SE with an invalid Connection ID",
> +	[27] = "the ISP_DMAC tried to process a SE with an invalid Remote Host interrupt",
> +	[28] = "a reserved opcode was detected in an SE",
> +	[29] = "received a SE Cpl with error status",
> +};
> +
> +struct chan_hw_regs {
> +	u16 cq_head;
> +	u16 rsvd1;
> +	u16 sq_tail;
> +	u16 rsvd2;
> +	u8 ctrl;
> +	u8 rsvd3[3];
> +	u16 status;
> +	u16 rsvd4;
> +};
> +
> +enum {
> +	PERF_BURST_SCALE = 0x1,
> +	PERF_BURST_SIZE = 0x6,
> +	PERF_INTERVAL = 0x0,
> +	PERF_MRRS = 0x3,
> +	PERF_ARB_WEIGHT = 0x1,
> +};
> +
> +enum {
> +	PERF_BURST_SCALE_SHIFT = 0x2,
> +	PERF_BURST_SCALE_MASK = 0x3,
> +	PERF_MRRS_SHIFT = 0x4,
> +	PERF_MRRS_MASK = 0x7,
> +	PERF_INTERVAL_SHIFT = 0x8,
> +	PERF_INTERVAL_MASK = 0x7,
> +	PERF_BURST_SIZE_SHIFT = 0xc,
> +	PERF_BURST_SIZE_MASK = 0x7,
> +	PERF_ARB_WEIGHT_SHIFT = 0x18,
> +	PERF_ARB_WEIGHT_MASK = 0xff,
> +};
> +
> +enum {
> +	PERF_MIN_INTERVAL = 0,
> +	PERF_MAX_INTERVAL = 0x7,
> +	PERF_MIN_BURST_SIZE = 0,
> +	PERF_MAX_BURST_SIZE = 0x7,
> +	PERF_MIN_BURST_SCALE = 0,
> +	PERF_MAX_BURST_SCALE = 0x2,
> +	PERF_MIN_MRRS = 0,
> +	PERF_MAX_MRRS = 0x7,
> +};
> +
> +enum {
> +	SE_BUF_BASE_SHIFT = 0x2,
> +	SE_BUF_BASE_MASK = 0x1ff,
> +	SE_BUF_LEN_SHIFT = 0xc,
> +	SE_BUF_LEN_MASK = 0x1ff,
> +	SE_THRESH_SHIFT = 0x17,
> +	SE_THRESH_MASK = 0x1ff,
> +};
> +
> +#define SWITCHTEC_CHAN_ENABLE	BIT(1)
> +
> +struct chan_fw_regs {
> +	u32 valid_en_se;
> +	u32 cq_base_lo;
> +	u32 cq_base_hi;
> +	u16 cq_size;
> +	u16 rsvd1;
> +	u32 sq_base_lo;
> +	u32 sq_base_hi;
> +	u16 sq_size;
> +	u16 rsvd2;
> +	u32 int_vec;
> +	u32 perf_cfg;
> +	u32 rsvd3;
> +	u32 perf_latency_selector;
> +	u32 perf_fetched_se_cnt_lo;
> +	u32 perf_fetched_se_cnt_hi;
> +	u32 perf_byte_cnt_lo;
> +	u32 perf_byte_cnt_hi;
> +	u32 rsvd4;
> +	u16 perf_se_pending;
> +	u16 perf_se_buf_empty;
> +	u32 perf_chan_idle;
> +	u32 perf_lat_max;
> +	u32 perf_lat_min;
> +	u32 perf_lat_last;
> +	u16 sq_current;
> +	u16 sq_phase;
> +	u16 cq_current;
> +	u16 cq_phase;
> +};
> +
> +enum cmd {
> +	CMD_GET_HOST_LIST = 1,
> +	CMD_REGISTER_BUF = 2,
> +	CMD_UNREGISTER_BUF = 3,
> +	CMD_GET_BUF_LIST = 4,
> +	CMD_GET_OWN_BUF_LIST = 5,
> +};
> +
> +enum cmd_status {
> +	CMD_STATUS_IDLE = 0,
> +	CMD_STATUS_INPROGRESS = 0x1,
> +	CMD_STATUS_DONE = 0x2,
> +	CMD_STATUS_ERROR = 0xFF,
> +};
> +
> +struct switchtec_dma_chan {
> +	struct switchtec_dma_dev *swdma_dev;
> +	struct dma_chan dma_chan;
> +	struct chan_hw_regs __iomem *mmio_chan_hw;
> +	struct chan_fw_regs __iomem *mmio_chan_fw;
> +	spinlock_t hw_ctrl_lock;
> +
> +	struct tasklet_struct desc_task;
> +	spinlock_t submit_lock;
> +	bool ring_active;
> +	int cid;
> +	spinlock_t complete_lock;
> +	bool comp_ring_active;
> +
> +	/* channel index and irq */
> +	int index;
> +	int irq;
> +
> +	/*
> +	 * In driver context, head is advanced by producer while
> +	 * tail is advanced by consumer.
> +	 */
> +
> +	/* the head and tail for both desc_ring and hw_sq */
> +	int head;
> +	int tail;
> +	int phase_tag;
> +	struct switchtec_dma_desc **desc_ring;
> +	struct switchtec_dma_hw_se_desc *hw_sq;
> +	dma_addr_t dma_addr_sq;
> +
> +	/* the tail for hw_cq */
> +	int cq_tail;
> +	struct switchtec_dma_hw_ce *hw_cq;
> +	dma_addr_t dma_addr_cq;
> +
> +	struct list_head list;
> +};
> +
> +struct switchtec_dma_dev {
> +	struct dma_device dma_dev;
> +	struct pci_dev __rcu *pdev;
> +	struct switchtec_dma_chan **swdma_chans;
> +	int chan_cnt;
> +	int chan_status_irq;
> +	void __iomem *bar;
> +	struct tasklet_struct chan_status_task;
> +};
> +
> +static struct switchtec_dma_chan *to_switchtec_dma_chan(struct dma_chan *c)
> +{
> +	return container_of(c, struct switchtec_dma_chan, dma_chan);
> +}
> +
> +static struct device *to_chan_dev(struct switchtec_dma_chan *swdma_chan)
> +{
> +	return &swdma_chan->dma_chan.dev->device;
> +}
> +
> +enum switchtec_dma_opcode {
> +	SWITCHTEC_DMA_OPC_MEMCPY = 0,
> +	SWITCHTEC_DMA_OPC_RDIMM = 0x1,
> +	SWITCHTEC_DMA_OPC_WRIMM = 0x2,
> +	SWITCHTEC_DMA_OPC_RHI = 0x6,
> +	SWITCHTEC_DMA_OPC_NOP = 0x7,
> +};
> +
> +struct switchtec_dma_hw_se_desc {
> +	u8 opc;
> +	u8 ctrl;
> +	__le16 tlp_setting;
> +	__le16 rsvd1;
> +	__le16 cid;
> +	__le32 byte_cnt;
> +	__le32 addr_lo; /* SADDR_LO/WIADDR_LO */
> +	__le32 addr_hi; /* SADDR_HI/WIADDR_HI */
> +	__le32 daddr_lo;
> +	__le32 daddr_hi;
> +	__le16 dfid;
> +	__le16 sfid;
> +};
> +
> +#define SWITCHTEC_SE_DFM		BIT(5)
> +#define SWITCHTEC_SE_LIOF		BIT(6)
> +#define SWITCHTEC_SE_BRR		BIT(7)
> +#define SWITCHTEC_SE_CID_MASK		GENMASK(15, 0)
> +
> +#define SWITCHTEC_CE_SC_LEN_ERR		BIT(0)
> +#define SWITCHTEC_CE_SC_UR		BIT(1)
> +#define SWITCHTEC_CE_SC_CA		BIT(2)
> +#define SWITCHTEC_CE_SC_RSVD_CPL	BIT(3)
> +#define SWITCHTEC_CE_SC_ECRC_ERR	BIT(4)
> +#define SWITCHTEC_CE_SC_EP_SET		BIT(5)
> +#define SWITCHTEC_CE_SC_D_RD_CTO	BIT(8)
> +#define SWITCHTEC_CE_SC_D_RIMM_UR	BIT(9)
> +#define SWITCHTEC_CE_SC_D_RIMM_CA	BIT(10)
> +#define SWITCHTEC_CE_SC_D_RIMM_RSVD_CPL	BIT(11)
> +#define SWITCHTEC_CE_SC_D_ECRC		BIT(12)
> +#define SWITCHTEC_CE_SC_D_EP_SET	BIT(13)
> +#define SWITCHTEC_CE_SC_D_BAD_CONNID	BIT(14)
> +#define SWITCHTEC_CE_SC_D_BAD_RHI_ADDR	BIT(15)
> +#define SWITCHTEC_CE_SC_D_INVD_CMD	BIT(16)
> +#define SWITCHTEC_CE_SC_MASK		GENMASK(16, 0)
> +
> +struct switchtec_dma_hw_ce {
> +	__le32 rdimm_cpl_dw0;
> +	__le32 rdimm_cpl_dw1;
> +	__le32 rsvd1;
> +	__le32 cpl_byte_cnt;
> +	__le16 sq_head;
> +	__le16 rsvd2;
> +	__le32 rsvd3;
> +	__le32 sts_code;
> +	__le16 cid;
> +	__le16 phase_tag;
> +};
> +
> +struct switchtec_dma_desc {
> +	struct dma_async_tx_descriptor txd;
> +	struct switchtec_dma_hw_se_desc *hw;
> +	u32 orig_size;
> +	bool completed;
> +};
> +
> +#define SWITCHTEC_INVALID_HFID 0xffff
> +
> +enum desc_type {
> +	MEMCPY,
> +	WIMM,
> +	UNKNOWN_TRANSACTION,
> +};
> +
> +#define SWITCHTEC_DMA_SQ_SIZE	SZ_32K
> +#define SWITCHTEC_DMA_CQ_SIZE	SZ_32K
> +
> +#define SWITCHTEC_DMA_RING_SIZE	SWITCHTEC_DMA_SQ_SIZE
> +
> +static int wait_for_chan_status(struct chan_hw_regs __iomem *chan_hw, u32 mask,
> +		bool set)

single line would read much better! (here and few other places)

Also run checkpatch with --strict option, that will help catch style
inconsistencies (i am seeing some below)

> +{
> +	u32 status;
> +	int retry = 100;
> +	int ret = -EIO;
> +
> +	do {
> +		status = readl(&chan_hw->status);
> +		if ((set && (status & mask)) ||
> +		    (!set && !(status & mask))) {
> +			ret = 0;
> +			break;
> +		}

why not use readl_poll_timeout()

> +
> +		udelay(1000);
> +	} while (retry--);
> +
> +	return ret;
> +}
> +
> +static int halt_channel(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		ret = -ENODEV;
> +		goto unlock_and_exit;
> +	}
> +
> +	spin_lock(&swdma_chan->hw_ctrl_lock);
> +	writeb(SWITCHTEC_CHAN_CTRL_HALT, &chan_hw->ctrl);
> +	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_HALTED, true);
> +	spin_unlock(&swdma_chan->hw_ctrl_lock);
> +
> +unlock_and_exit:
> +	rcu_read_unlock();
> +	return ret;
> +}
> +
> +static int unhalt_channel(struct switchtec_dma_chan *swdma_chan)
> +{
> +	u8 ctrl;
> +	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		ret = -ENODEV;
> +		goto unlock_and_exit;
> +	}
> +
> +	spin_lock(&swdma_chan->hw_ctrl_lock);
> +	ctrl = readb(&chan_hw->ctrl);
> +	ctrl &= ~SWITCHTEC_CHAN_CTRL_HALT;
> +	writeb(ctrl, &chan_hw->ctrl);
> +	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_HALTED, false);
> +	spin_unlock(&swdma_chan->hw_ctrl_lock);
> +
> +unlock_and_exit:
> +	rcu_read_unlock();
> +	return ret;
> +}
> +
> +static void flush_pci_write(struct chan_hw_regs __iomem *chan_hw)
> +{
> +	readl(&chan_hw->cq_head);
> +}
> +
> +static int reset_channel(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
> +	struct pci_dev *pdev;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +
> +	spin_lock(&swdma_chan->hw_ctrl_lock);
> +	writel(SWITCHTEC_CHAN_CTRL_RESET | SWITCHTEC_CHAN_CTRL_ERR_PAUSE,
> +	       &chan_hw->ctrl);
> +	flush_pci_write(chan_hw);
> +
> +	udelay(1000);
> +
> +	writel(SWITCHTEC_CHAN_CTRL_ERR_PAUSE, &chan_hw->ctrl);
> +	spin_unlock(&swdma_chan->hw_ctrl_lock);
> +	flush_pci_write(chan_hw);
> +
> +	rcu_read_unlock();
> +	return 0;
> +}
> +
> +static int pause_reset_channel(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
> +	struct pci_dev *pdev;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +
> +	spin_lock(&swdma_chan->hw_ctrl_lock);
> +	writeb(SWITCHTEC_CHAN_CTRL_PAUSE, &chan_hw->ctrl);
> +	spin_unlock(&swdma_chan->hw_ctrl_lock);
> +
> +	flush_pci_write(chan_hw);
> +
> +	rcu_read_unlock();
> +
> +	/* wait 60ms to ensure no pending CEs */
> +	mdelay(60);
> +
> +	return reset_channel(swdma_chan);
> +

drop the empty line here

> +}
> +
> +static int switchtec_dma_pause(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		ret = -ENODEV;
> +		goto unlock_and_exit;
> +	}
> +
> +	spin_lock(&swdma_chan->hw_ctrl_lock);
> +	writeb(SWITCHTEC_CHAN_CTRL_PAUSE, &chan_hw->ctrl);
> +	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_PAUSED, true);
> +	spin_unlock(&swdma_chan->hw_ctrl_lock);
> +
> +unlock_and_exit:
> +	rcu_read_unlock();
> +	return ret;
> +}
> +
> +static int switchtec_dma_resume(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		ret = -ENODEV;
> +		goto unlock_and_exit;
> +	}
> +
> +	spin_lock(&swdma_chan->hw_ctrl_lock);
> +	writeb(0, &chan_hw->ctrl);
> +	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_PAUSED, false);
> +	spin_unlock(&swdma_chan->hw_ctrl_lock);
> +
> +unlock_and_exit:
> +	rcu_read_unlock();
> +	return ret;
> +}
> +
> +static int enable_channel(struct switchtec_dma_chan *swdma_chan)
> +{
> +	u32 valid_en_se;
> +	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
> +	struct pci_dev *pdev;

reverse christmas tree pls

> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +
> +	valid_en_se = readl(&chan_fw->valid_en_se);
> +	valid_en_se |= SWITCHTEC_CHAN_ENABLE;
> +
> +	writel(valid_en_se, &chan_fw->valid_en_se);
> +
> +	rcu_read_unlock();
> +	return 0;
> +}
> +
> +static int disable_channel(struct switchtec_dma_chan *swdma_chan)
> +{
> +	u32 valid_en_se;
> +	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
> +	struct pci_dev *pdev;
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +	if (!pdev) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +
> +	valid_en_se = readl(&chan_fw->valid_en_se);
> +	valid_en_se &= ~SWITCHTEC_CHAN_ENABLE;
> +
> +	writel(valid_en_se, &chan_fw->valid_en_se);
> +
> +	rcu_read_unlock();
> +	return 0;

only diff b/w enable/disable is bit ops, I guess we can have a common fn
with argument for enable/disable

> +}
> +
> +static struct switchtec_dma_desc *switchtec_dma_get_desc(
> +		struct switchtec_dma_chan *swdma_chan, int i)
> +{
> +	return swdma_chan->desc_ring[i];
> +}
> +
> +static struct switchtec_dma_hw_ce *switchtec_dma_get_ce(
> +		struct switchtec_dma_chan *swdma_chan, int i)
> +{
> +	return &swdma_chan->hw_cq[i];
> +}
> +
> +static void switchtec_dma_process_desc(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct device *chan_dev = to_chan_dev(swdma_chan);
> +	struct dmaengine_result res;
> +	struct switchtec_dma_desc *desc;
> +	struct switchtec_dma_hw_ce *ce;
> +	__le16 phase_tag;
> +	int tail;
> +	int cid;
> +	int se_idx;
> +	u32 sts_code;
> +	int i;
> +	__le32 *p;
> +
> +	do {
> +		spin_lock_bh(&swdma_chan->complete_lock);
> +		if (!swdma_chan->comp_ring_active) {
> +			spin_unlock_bh(&swdma_chan->complete_lock);
> +			break;
> +		}
> +
> +		ce = switchtec_dma_get_ce(swdma_chan, swdma_chan->cq_tail);
> +
> +		/*
> +		 * phase_tag is updated by hardware, ensure the value is
> +		 * not from the cache
> +		 */
> +		phase_tag = smp_load_acquire(&ce->phase_tag);
> +		if (le16_to_cpu(phase_tag) == swdma_chan->phase_tag) {
> +			spin_unlock_bh(&swdma_chan->complete_lock);
> +			break;
> +		}
> +
> +		cid = le16_to_cpu(ce->cid);
> +		se_idx = cid & (SWITCHTEC_DMA_SQ_SIZE - 1);
> +		desc = switchtec_dma_get_desc(swdma_chan, se_idx);
> +
> +		tail = swdma_chan->tail;
> +
> +		res.residue = desc->orig_size - le32_to_cpu(ce->cpl_byte_cnt);
> +
> +		sts_code = le32_to_cpu(ce->sts_code);
> +
> +		if (!(sts_code & SWITCHTEC_CE_SC_MASK)) {
> +			res.result = DMA_TRANS_NOERROR;
> +		} else {
> +			if (sts_code & SWITCHTEC_CE_SC_D_RD_CTO)
> +				res.result = DMA_TRANS_READ_FAILED;
> +			else
> +				res.result = DMA_TRANS_WRITE_FAILED;
> +
> +			dev_err(chan_dev, "CID 0x%04x failed, SC 0x%08x\n", cid,
> +				(u32)(sts_code & SWITCHTEC_CE_SC_MASK));
> +
> +			p = (__le32 *)ce;
> +			for (i = 0; i < sizeof(*ce)/4; i++) {
> +				dev_err(chan_dev, "CE DW%d: 0x%08x\n", i,
> +					le32_to_cpu(*p));
> +				p++;
> +			}
> +		}
> +
> +		desc->completed = true;
> +
> +		swdma_chan->cq_tail++;
> +		swdma_chan->cq_tail &= SWITCHTEC_DMA_CQ_SIZE - 1;
> +
> +		rcu_read_lock();
> +		if (!rcu_dereference(swdma_chan->swdma_dev->pdev)) {
> +			rcu_read_unlock();
> +			spin_unlock_bh(&swdma_chan->complete_lock);
> +			return;
> +		}
> +		writew(swdma_chan->cq_tail, &swdma_chan->mmio_chan_hw->cq_head);
> +		rcu_read_unlock();
> +
> +		if (swdma_chan->cq_tail == 0)
> +			swdma_chan->phase_tag = !swdma_chan->phase_tag;
> +
> +		/*  Out of order CE */
> +		if (se_idx != tail) {
> +			spin_unlock_bh(&swdma_chan->complete_lock);
> +			continue;
> +		}
> +
> +		do {
> +			dma_cookie_complete(&desc->txd);
> +			dma_descriptor_unmap(&desc->txd);
> +			dmaengine_desc_get_callback_invoke(&desc->txd, &res);
> +			desc->txd.callback = NULL;
> +			desc->txd.callback_result = NULL;
> +			desc->completed = false;
> +
> +			tail++;
> +			tail &= SWITCHTEC_DMA_SQ_SIZE - 1;
> +
> +			/*
> +			 * Ensure the desc updates are visible before updating
> +			 * the tail index
> +			 */
> +			smp_store_release(&swdma_chan->tail, tail);
> +			desc = switchtec_dma_get_desc(swdma_chan,
> +						      swdma_chan->tail);
> +			if (!desc->completed)
> +				break;
> +		} while (CIRC_CNT(READ_ONCE(swdma_chan->head), swdma_chan->tail,
> +				  SWITCHTEC_DMA_SQ_SIZE));
> +
> +		spin_unlock_bh(&swdma_chan->complete_lock);
> +	} while (1);
> +}
> +
> +static void switchtec_dma_abort_desc(struct switchtec_dma_chan *swdma_chan,
> +		int force)
> +{
> +	struct dmaengine_result res;
> +	struct switchtec_dma_desc *desc;
> +
> +	if (!force)
> +		switchtec_dma_process_desc(swdma_chan);
> +
> +	spin_lock_bh(&swdma_chan->complete_lock);
> +
> +	while (CIRC_CNT(swdma_chan->head, swdma_chan->tail,
> +			SWITCHTEC_DMA_SQ_SIZE) >= 1) {
> +		desc = switchtec_dma_get_desc(swdma_chan, swdma_chan->tail);
> +
> +		res.residue = desc->orig_size;
> +		res.result = DMA_TRANS_ABORTED;
> +
> +		dma_cookie_complete(&desc->txd);
> +		dma_descriptor_unmap(&desc->txd);
> +		if (!force)
> +			dmaengine_desc_get_callback_invoke(&desc->txd, &res);
> +		desc->txd.callback = NULL;
> +		desc->txd.callback_result = NULL;
> +
> +		swdma_chan->tail++;
> +		swdma_chan->tail &= SWITCHTEC_DMA_SQ_SIZE - 1;
> +	}
> +
> +	spin_unlock_bh(&swdma_chan->complete_lock);
> +}
> +
> +static void switchtec_dma_chan_stop(struct switchtec_dma_chan *swdma_chan)
> +{
> +	int rc;
> +
> +	rc = halt_channel(swdma_chan);
> +	if (rc)
> +		return;
> +
> +	rcu_read_lock();
> +	if (!rcu_dereference(swdma_chan->swdma_dev->pdev)) {
> +		rcu_read_unlock();
> +		return;
> +	}
> +
> +	writel(0, &swdma_chan->mmio_chan_fw->sq_base_lo);
> +	writel(0, &swdma_chan->mmio_chan_fw->sq_base_hi);
> +	writel(0, &swdma_chan->mmio_chan_fw->cq_base_lo);
> +	writel(0, &swdma_chan->mmio_chan_fw->cq_base_hi);
> +
> +	rcu_read_unlock();
> +}
> +
> +static int switchtec_dma_terminate_all(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +
> +	spin_lock_bh(&swdma_chan->complete_lock);
> +	swdma_chan->comp_ring_active = false;
> +	spin_unlock_bh(&swdma_chan->complete_lock);
> +
> +	return pause_reset_channel(swdma_chan);
> +}
> +
> +static void switchtec_dma_synchronize(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +	int rc;
> +
> +	switchtec_dma_abort_desc(swdma_chan, 1);
> +
> +	rc = enable_channel(swdma_chan);
> +	if (rc)
> +		return;
> +
> +	rc = reset_channel(swdma_chan);
> +	if (rc)
> +		return;
> +
> +	rc = unhalt_channel(swdma_chan);
> +	if (rc)
> +		return;
> +
> +	spin_lock_bh(&swdma_chan->submit_lock);
> +	swdma_chan->head = 0;
> +	spin_unlock_bh(&swdma_chan->submit_lock);
> +
> +	spin_lock_bh(&swdma_chan->complete_lock);
> +	swdma_chan->comp_ring_active = true;
> +	swdma_chan->phase_tag = 0;
> +	swdma_chan->tail = 0;
> +	swdma_chan->cq_tail = 0;
> +	swdma_chan->cid = 0;
> +	dma_cookie_init(chan);
> +	spin_unlock_bh(&swdma_chan->complete_lock);
> +}
> +
> +static void switchtec_dma_desc_task(unsigned long data)
> +{
> +	struct switchtec_dma_chan *swdma_chan = (void *)data;
> +
> +	switchtec_dma_process_desc(swdma_chan);
> +}
> +
> +static void switchtec_dma_chan_status_task(unsigned long data)
> +{
> +	struct switchtec_dma_dev *swdma_dev = (void *)data;
> +	struct dma_device *dma_dev = &swdma_dev->dma_dev;
> +	struct dma_chan *chan;
> +	struct switchtec_dma_chan *swdma_chan;
> +	struct chan_hw_regs __iomem *chan_hw;
> +	struct device *chan_dev;
> +	u32 chan_status;
> +	int bit;
> +
> +	list_for_each_entry(chan, &dma_dev->channels, device_node) {
> +		swdma_chan = to_switchtec_dma_chan(chan);
> +		chan_dev = to_chan_dev(swdma_chan);
> +		chan_hw = swdma_chan->mmio_chan_hw;
> +
> +		rcu_read_lock();
> +		if (!rcu_dereference(swdma_dev->pdev)) {
> +			rcu_read_unlock();
> +			return;
> +		}
> +
> +		chan_status = readl(&chan_hw->status);
> +		chan_status &= SWITCHTEC_CHAN_STS_PAUSED_MASK;
> +		rcu_read_unlock();
> +
> +		bit = ffs(chan_status);
> +		if (!bit)
> +			dev_dbg(chan_dev, "No pause bit set.");
> +		else
> +			dev_err(chan_dev, "Paused, %s\n",
> +				channel_status_str[bit - 1]);
> +	}
> +}
> +
> +static struct dma_async_tx_descriptor *switchtec_dma_prep_desc(
> +		struct dma_chan *c, enum desc_type type, u16 dst_fid,
> +		dma_addr_t dma_dst, u16 src_fid, dma_addr_t dma_src, u64 data,
> +		size_t len, unsigned long flags)
> +	__acquires(swdma_chan->submit_lock)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(c);
> +	struct switchtec_dma_desc *desc;
> +	int head;
> +	int tail;
> +
> +
> +	if (type != MEMCPY && type != WIMM) {
> +		/*
> +		 * Keep sparse happy by restoring an even lock count on
> +		 * this lock.
> +		 */
> +		__acquire(swdma_chan->submit_lock);
> +		return NULL;
> +	}
> +
> +	spin_lock_bh(&swdma_chan->submit_lock);
> +
> +	if (!swdma_chan->ring_active)
> +		goto err_unlock;
> +
> +	tail = READ_ONCE(swdma_chan->tail);
> +	head = swdma_chan->head;
> +
> +	if (!CIRC_SPACE(head, tail, SWITCHTEC_DMA_RING_SIZE))
> +		goto err_unlock;
> +
> +	desc = switchtec_dma_get_desc(swdma_chan, head);
> +
> +	if (src_fid != SWITCHTEC_INVALID_HFID &&
> +	    dst_fid != SWITCHTEC_INVALID_HFID)
> +		desc->hw->ctrl |= SWITCHTEC_SE_DFM;
> +
> +	if (flags & DMA_PREP_INTERRUPT)
> +		desc->hw->ctrl |= SWITCHTEC_SE_LIOF;
> +
> +	if (flags & DMA_PREP_FENCE)
> +		desc->hw->ctrl |= SWITCHTEC_SE_BRR;
> +
> +	desc->txd.flags = flags;
> +
> +	desc->completed = false;
> +	if (type == MEMCPY) {
> +		desc->hw->opc = SWITCHTEC_DMA_OPC_MEMCPY;
> +		desc->hw->addr_lo = cpu_to_le32(lower_32_bits(dma_src));
> +		desc->hw->addr_hi = cpu_to_le32(upper_32_bits(dma_src));
> +	} else {
> +		desc->hw->opc = SWITCHTEC_DMA_OPC_WRIMM;
> +		desc->hw->addr_lo = cpu_to_le32(lower_32_bits(data));
> +		desc->hw->addr_hi = cpu_to_le32(upper_32_bits(data));
> +	}
> +	desc->hw->daddr_lo = cpu_to_le32(lower_32_bits(dma_dst));
> +	desc->hw->daddr_hi = cpu_to_le32(upper_32_bits(dma_dst));
> +	desc->hw->byte_cnt = cpu_to_le32(len);
> +	desc->hw->tlp_setting = 0;
> +	desc->hw->dfid = cpu_to_le16(dst_fid);
> +	desc->hw->sfid = cpu_to_le16(src_fid);
> +	swdma_chan->cid &= SWITCHTEC_SE_CID_MASK;
> +	desc->hw->cid = cpu_to_le16(swdma_chan->cid++);
> +	desc->orig_size = len;
> +
> +	head++;
> +	head &= SWITCHTEC_DMA_RING_SIZE - 1;
> +
> +	/*
> +	 * Ensure the desc updates are visible before updating the head index
> +	 */
> +	smp_store_release(&swdma_chan->head, head);
> +
> +	/* return with the lock held, it will be released in tx_submit */
> +
> +	return &desc->txd;
> +
> +err_unlock:
> +	/*
> +	 * Keep sparse happy by restoring an even lock count on
> +	 * this lock.
> +	 */
> +	__acquire(swdma_chan->submit_lock);
> +
> +	spin_unlock_bh(&swdma_chan->submit_lock);
> +	return NULL;
> +}
> +
> +static struct dma_async_tx_descriptor *switchtec_dma_prep_memcpy(
> +		struct dma_chan *c, dma_addr_t dma_dst, dma_addr_t dma_src,
> +		size_t len, unsigned long flags)
> +	__acquires(swdma_chan->submit_lock)
> +{
> +	if (len > SWITCHTEC_DESC_MAX_SIZE) {
> +		/*
> +		 * Keep sparse happy by restoring an even lock count on
> +		 * this lock.
> +		 */
> +		__acquire(swdma_chan->submit_lock);
> +		return NULL;
> +	}
> +
> +	return switchtec_dma_prep_desc(c, MEMCPY, SWITCHTEC_INVALID_HFID,
> +				       dma_dst, SWITCHTEC_INVALID_HFID, dma_src,
> +				       0, len, flags);
> +}
> +
> +static struct dma_async_tx_descriptor *switchtec_dma_prep_wimm_data(
> +		struct dma_chan *c, dma_addr_t dma_dst, u64 data,
> +		unsigned long flags)
> +	__acquires(swdma_chan->submit_lock)
> +{

can you please explain what is meant by wimm data and how it us used?

> +	size_t len = sizeof(data);
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(c);
> +	struct device *chan_dev = to_chan_dev(swdma_chan);
> +
> +	if ((len == 8) && (dma_dst & ((1 << DMAENGINE_ALIGN_8_BYTES) - 1))) {
> +		dev_err(chan_dev,
> +			"QW WIMM dst addr 0x%08x_%08x not QW aligned!\n",
> +			upper_32_bits(dma_dst), lower_32_bits(dma_dst));
> +		/*
> +		 * Keep sparse happy by restoring an even lock count on
> +		 * this lock.
> +		 */
> +		__acquire(swdma_chan->submit_lock);
> +		return NULL;
> +	}
> +
> +	return switchtec_dma_prep_desc(c, WIMM, SWITCHTEC_INVALID_HFID, dma_dst,
> +				       SWITCHTEC_INVALID_HFID, 0, data, len,
> +				       flags);
> +}
> +
> +static dma_cookie_t switchtec_dma_tx_submit(
> +		struct dma_async_tx_descriptor *desc)
> +	__releases(swdma_chan->submit_lock)
> +{
> +	struct switchtec_dma_chan *swdma_chan =
> +		to_switchtec_dma_chan(desc->chan);
> +	dma_cookie_t cookie;
> +
> +	cookie = dma_cookie_assign(desc);
> +
> +	spin_unlock_bh(&swdma_chan->submit_lock);

I dont this is correct, why would you prevent users from preparing
multiple descriptors..?

> +
> +	return cookie;
> +}
> +
> +static enum dma_status switchtec_dma_tx_status(struct dma_chan *chan,
> +		dma_cookie_t cookie, struct dma_tx_state *txstate)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +	enum dma_status ret;
> +
> +	ret = dma_cookie_status(chan, cookie, txstate);
> +	if (ret == DMA_COMPLETE)
> +		return ret;
> +
> +	switchtec_dma_process_desc(swdma_chan);
> +
> +	return dma_cookie_status(chan, cookie, txstate);
> +}
> +
> +static void switchtec_dma_issue_pending(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
> +
> +	/*
> +	 * Ensure the desc updates are visible before starting the
> +	 * DMA engine.
> +	 */
> +	wmb();
> +
> +	/*
> +	 * The sq_tail register is actually for the head of the
> +	 * submisssion queue. Chip has the opposite define of head/tail
> +	 * to the Linux kernel.
> +	 */
> +
> +	rcu_read_lock();
> +	if (!rcu_dereference(swdma_dev->pdev)) {
> +		rcu_read_unlock();
> +		return;
> +	}
> +
> +	spin_lock_bh(&swdma_chan->submit_lock);
> +	writew(swdma_chan->head, &swdma_chan->mmio_chan_hw->sq_tail);
> +	spin_unlock_bh(&swdma_chan->submit_lock);
> +
> +	rcu_read_unlock();
> +}
> +
> +static irqreturn_t switchtec_dma_isr(int irq, void *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = chan;
> +
> +	if (swdma_chan->comp_ring_active)
> +		tasklet_schedule(&swdma_chan->desc_task);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t switchtec_dma_chan_status_isr(int irq, void *dma)
> +{
> +	struct switchtec_dma_dev *swdma_dev = dma;
> +
> +	tasklet_schedule(&swdma_dev->chan_status_task);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void switchtec_dma_free_desc(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
> +	size_t size;
> +	int i;
> +
> +	size = SWITCHTEC_DMA_SQ_SIZE * sizeof(*swdma_chan->hw_sq);
> +	if (swdma_chan->hw_sq)
> +		dma_free_coherent(swdma_dev->dma_dev.dev, size,
> +				  swdma_chan->hw_sq, swdma_chan->dma_addr_sq);
> +
> +	size = SWITCHTEC_DMA_CQ_SIZE * sizeof(*swdma_chan->hw_cq);
> +	if (swdma_chan->hw_cq)
> +		dma_free_coherent(swdma_dev->dma_dev.dev, size,
> +				  swdma_chan->hw_cq, swdma_chan->dma_addr_cq);
> +
> +	if (swdma_chan->desc_ring) {
> +		for (i = 0; i < SWITCHTEC_DMA_RING_SIZE; i++)
> +			kfree(swdma_chan->desc_ring[i]);
> +
> +		kfree(swdma_chan->desc_ring);
> +	}
> +}
> +
> +static int switchtec_dma_alloc_desc(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
> +	struct pci_dev *pdev;
> +	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
> +	size_t size;
> +	struct switchtec_dma_desc *desc;
> +	int rc;
> +	int i;
> +
> +	swdma_chan->head = swdma_chan->tail = 0;
> +	swdma_chan->cq_tail = 0;
> +
> +	size = SWITCHTEC_DMA_SQ_SIZE * sizeof(*swdma_chan->hw_sq);
> +	swdma_chan->hw_sq = dma_alloc_coherent(swdma_dev->dma_dev.dev, size,
> +					       &swdma_chan->dma_addr_sq,
> +					       GFP_KERNEL);

this can be called from atomic context, GFP_NOWAIT pls

> +	if (!swdma_chan->hw_sq) {
> +		rc = -ENOMEM;
> +		goto free_and_exit;
> +	}
> +
> +	size = SWITCHTEC_DMA_CQ_SIZE * sizeof(*swdma_chan->hw_cq);
> +	swdma_chan->hw_cq = dma_alloc_coherent(swdma_dev->dma_dev.dev, size,
> +					       &swdma_chan->dma_addr_cq,
> +					       GFP_KERNEL);
> +	if (!swdma_chan->hw_cq) {
> +		rc = -ENOMEM;
> +		goto free_and_exit;
> +	}
> +
> +	/* reset host phase tag */
> +	swdma_chan->phase_tag = 0;
> +
> +	size = sizeof(*swdma_chan->desc_ring);
> +	swdma_chan->desc_ring = kcalloc(SWITCHTEC_DMA_RING_SIZE, size,
> +					GFP_KERNEL);
> +	if (!swdma_chan->desc_ring) {
> +		rc = -ENOMEM;
> +		goto free_and_exit;
> +	}
> +
> +	for (i = 0; i < SWITCHTEC_DMA_RING_SIZE; i++) {
> +		desc = kzalloc(sizeof(*desc), GFP_KERNEL);
> +		if (!desc) {
> +			rc = -ENOMEM;
> +			goto free_and_exit;
> +		}
> +
> +		dma_async_tx_descriptor_init(&desc->txd, &swdma_chan->dma_chan);
> +		desc->txd.tx_submit = switchtec_dma_tx_submit;
> +		desc->hw = &swdma_chan->hw_sq[i];
> +		desc->completed = true;
> +
> +		swdma_chan->desc_ring[i] = desc;
> +	}
> +
> +	rcu_read_lock();
> +	pdev = rcu_dereference(swdma_dev->pdev);
> +	if (!pdev) {
> +		rcu_read_unlock();
> +		rc = -ENODEV;
> +		goto free_and_exit;
> +	}
> +
> +	/* set sq/cq */
> +	writel(lower_32_bits(swdma_chan->dma_addr_sq), &chan_fw->sq_base_lo);
> +	writel(upper_32_bits(swdma_chan->dma_addr_sq), &chan_fw->sq_base_hi);
> +	writel(lower_32_bits(swdma_chan->dma_addr_cq), &chan_fw->cq_base_lo);
> +	writel(upper_32_bits(swdma_chan->dma_addr_cq), &chan_fw->cq_base_hi);
> +
> +	writew(SWITCHTEC_DMA_SQ_SIZE, &swdma_chan->mmio_chan_fw->sq_size);
> +	writew(SWITCHTEC_DMA_CQ_SIZE, &swdma_chan->mmio_chan_fw->cq_size);

why is hardware being written in alloc call, the job is to prepare
descritor, hw write should happen when we submit the descriptors..

> +
> +	rcu_read_unlock();
> +	return 0;
> +
> +free_and_exit:
> +	switchtec_dma_free_desc(swdma_chan);
> +	return rc;
> +}
> +
> +static int switchtec_dma_alloc_chan_resources(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
> +	u32 perf_cfg;
> +	int rc;
> +
> +	rc = switchtec_dma_alloc_desc(swdma_chan);
> +	if (rc)
> +		return rc;
> +
> +	rc = enable_channel(swdma_chan);
> +	if (rc)
> +		return rc;
> +
> +	rc = reset_channel(swdma_chan);
> +	if (rc)
> +		return rc;
> +
> +	rc = unhalt_channel(swdma_chan);
> +	if (rc)
> +		return rc;
> +
> +	swdma_chan->ring_active = true;
> +	swdma_chan->comp_ring_active = true;
> +	swdma_chan->cid = 0;
> +
> +	dma_cookie_init(chan);
> +
> +	rcu_read_lock();
> +	if (!rcu_dereference(swdma_dev->pdev)) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +
> +	perf_cfg = readl(&swdma_chan->mmio_chan_fw->perf_cfg);
> +	rcu_read_unlock();
> +
> +	dev_dbg(&chan->dev->device, "Burst Size:  0x%x",
> +		(perf_cfg >> PERF_BURST_SIZE_SHIFT) & PERF_BURST_SIZE_MASK);
> +
> +	dev_dbg(&chan->dev->device, "Burst Scale: 0x%x",
> +		(perf_cfg >> PERF_BURST_SCALE_SHIFT) & PERF_BURST_SCALE_MASK);
> +
> +	dev_dbg(&chan->dev->device, "Interval:    0x%x",
> +		(perf_cfg >> PERF_INTERVAL_SHIFT) & PERF_INTERVAL_MASK);
> +
> +	dev_dbg(&chan->dev->device, "Arb Weight:  0x%x",
> +		(perf_cfg >> PERF_ARB_WEIGHT_SHIFT) & PERF_ARB_WEIGHT_MASK);
> +
> +	dev_dbg(&chan->dev->device, "MRRS:        0x%x",
> +		(perf_cfg >> PERF_MRRS_SHIFT) & PERF_MRRS_MASK);
> +
> +	return SWITCHTEC_DMA_SQ_SIZE;
> +}
> +
> +static void switchtec_dma_free_chan_resources(struct dma_chan *chan)
> +{
> +	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
> +
> +	spin_lock_bh(&swdma_chan->submit_lock);
> +	swdma_chan->ring_active = false;
> +	spin_unlock_bh(&swdma_chan->submit_lock);
> +
> +	spin_lock_bh(&swdma_chan->complete_lock);
> +	swdma_chan->comp_ring_active = false;
> +	spin_unlock_bh(&swdma_chan->complete_lock);
> +
> +	switchtec_dma_chan_stop(swdma_chan);
> +
> +	tasklet_kill(&swdma_chan->desc_task);
> +
> +	switchtec_dma_abort_desc(swdma_chan, 0);
> +
> +	switchtec_dma_free_desc(swdma_chan);
> +
> +	disable_channel(swdma_chan);
> +}
> +
> +static int switchtec_dma_chan_init(struct switchtec_dma_dev *swdma_dev, int i)
> +{
> +	struct dma_device *dma = &swdma_dev->dma_dev;
> +	struct pci_dev *pdev = rcu_dereference(swdma_dev->pdev);
> +	struct dma_chan *chan;
> +	struct switchtec_dma_chan *swdma_chan;
> +	u32 perf_cfg;
> +	u32 valid_en_se;
> +	u32 thresh;
> +	int se_buf_len;
> +	int irq;
> +	int rc;
> +
> +	swdma_chan = kzalloc(sizeof(*swdma_chan), GFP_KERNEL);
> +	if (!swdma_chan)
> +		return -ENOMEM;
> +
> +	swdma_chan->phase_tag = 0;
> +	swdma_chan->index = i;
> +	swdma_chan->swdma_dev = swdma_dev;
> +
> +	swdma_chan->mmio_chan_fw =
> +		swdma_dev->bar + SWITCHTEC_DMAC_CHAN_CFG_STS_OFFSET +
> +		i * SWITCHTEC_DMA_CHAN_FW_REGS_SIZE;
> +	swdma_chan->mmio_chan_hw =
> +		swdma_dev->bar + SWITCHTEC_DMAC_CHAN_CTRL_OFFSET +
> +		i * SWITCHTEC_DMA_CHAN_HW_REGS_SIZE;
> +
> +	swdma_dev->swdma_chans[i] = swdma_chan;
> +
> +	rc = pause_reset_channel(swdma_chan);
> +	if (rc)
> +		goto free_and_exit;
> +
> +	perf_cfg = readl(&swdma_chan->mmio_chan_fw->perf_cfg);
> +
> +	/* init perf tuner */
> +	perf_cfg = PERF_BURST_SCALE << PERF_BURST_SCALE_SHIFT;
> +	perf_cfg |= PERF_MRRS << PERF_MRRS_SHIFT;
> +	perf_cfg |= PERF_INTERVAL << PERF_INTERVAL_SHIFT;
> +	perf_cfg |= PERF_BURST_SIZE << PERF_BURST_SIZE_SHIFT;
> +	perf_cfg |= PERF_ARB_WEIGHT << PERF_ARB_WEIGHT_SHIFT;
> +
> +	writel(perf_cfg, &swdma_chan->mmio_chan_fw->perf_cfg);
> +
> +	valid_en_se = readl(&swdma_chan->mmio_chan_fw->valid_en_se);
> +
> +	dev_dbg(&pdev->dev, "Channel %d: SE buffer base %d\n",
> +		i, (valid_en_se >> SE_BUF_BASE_SHIFT) & SE_BUF_BASE_MASK);
> +
> +	se_buf_len = (valid_en_se >> SE_BUF_LEN_SHIFT) & SE_BUF_LEN_MASK;
> +	dev_dbg(&pdev->dev, "Channel %d: SE buffer count %d\n", i, se_buf_len);
> +
> +	thresh = se_buf_len / 2;
> +	valid_en_se |= (thresh & SE_THRESH_MASK) << SE_THRESH_SHIFT;
> +	writel(valid_en_se, &swdma_chan->mmio_chan_fw->valid_en_se);
> +
> +	/* request irqs */
> +	irq = readl(&swdma_chan->mmio_chan_fw->int_vec);
> +	dev_dbg(&pdev->dev, "Channel %d: CE irq vector %d\n", i, irq);
> +
> +	rc = pci_request_irq(pdev, irq, switchtec_dma_isr, NULL, swdma_chan,
> +			     KBUILD_MODNAME);
> +	if (rc)
> +		goto free_and_exit;
> +
> +	swdma_chan->irq = irq;
> +
> +	spin_lock_init(&swdma_chan->hw_ctrl_lock);
> +	spin_lock_init(&swdma_chan->submit_lock);
> +	spin_lock_init(&swdma_chan->complete_lock);
> +	tasklet_init(&swdma_chan->desc_task, switchtec_dma_desc_task,
> +		     (unsigned long)swdma_chan);
> +
> +	chan = &swdma_chan->dma_chan;
> +	chan->device = dma;
> +	dma_cookie_init(chan);
> +
> +	list_add_tail(&chan->device_node, &dma->channels);
> +
> +	return 0;
> +
> +free_and_exit:
> +	kfree(swdma_chan);
> +	return rc;
> +}
> +
> +static int switchtec_dma_chan_free(struct switchtec_dma_chan *swdma_chan)
> +{
> +	struct pci_dev *pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> +
> +	spin_lock_bh(&swdma_chan->submit_lock);
> +	swdma_chan->ring_active = false;
> +	spin_unlock_bh(&swdma_chan->submit_lock);
> +
> +	spin_lock_bh(&swdma_chan->complete_lock);
> +	swdma_chan->comp_ring_active = false;
> +	spin_unlock_bh(&swdma_chan->complete_lock);
> +
> +	pci_free_irq(pdev, swdma_chan->irq, swdma_chan);
> +
> +	switchtec_dma_chan_stop(swdma_chan);
> +
> +	return 0;
> +}
> +
> +static int switchtec_dma_chans_release(struct switchtec_dma_dev *swdma_dev)
> +{
> +	int i;
> +
> +	for (i = 0; i < swdma_dev->chan_cnt; i++)
> +		switchtec_dma_chan_free(swdma_dev->swdma_chans[i]);
> +
> +	return 0;
> +}
> +
> +static int switchtec_dma_chans_enumerate(struct switchtec_dma_dev *swdma_dev,
> +					 int chan_cnt)
> +{
> +	struct dma_device *dma = &swdma_dev->dma_dev;
> +	struct pci_dev *pdev = rcu_dereference(swdma_dev->pdev);
> +	int base;
> +	int cnt;
> +	int rc;
> +	int i;
> +
> +	swdma_dev->swdma_chans = kcalloc(chan_cnt,
> +					 sizeof(*swdma_dev->swdma_chans),
> +					 GFP_KERNEL);
> +
> +	if (!swdma_dev->swdma_chans)
> +		return -ENOMEM;
> +
> +	base = readw(swdma_dev->bar + SWITCHTEC_REG_SE_BUF_BASE);
> +	cnt = readw(swdma_dev->bar + SWITCHTEC_REG_SE_BUF_CNT);
> +
> +	dev_dbg(&pdev->dev, "EP SE buffer base %d\n", base);
> +	dev_dbg(&pdev->dev, "EP SE buffer count %d\n", cnt);
> +
> +	INIT_LIST_HEAD(&dma->channels);
> +
> +	for (i = 0; i < chan_cnt; i++) {
> +		rc = switchtec_dma_chan_init(swdma_dev, i);
> +		if (rc) {
> +			dev_err(&pdev->dev, "Channel %d: init channel failed\n",
> +				i);
> +			chan_cnt = i;
> +			goto err_exit;
> +		}
> +	}
> +
> +	return chan_cnt;
> +
> +err_exit:
> +	for (i = 0; i < chan_cnt; i++)
> +		switchtec_dma_chan_free(swdma_dev->swdma_chans[i]);
> +
> +	kfree(swdma_dev->swdma_chans);
> +
> +	return rc;
> +}
> +
> +static void switchtec_dma_release(struct dma_device *dma_dev)
> +{
> +	int i;
> +	struct switchtec_dma_dev *swdma_dev =
> +		container_of(dma_dev, struct switchtec_dma_dev, dma_dev);
> +
> +	for (i = 0; i < swdma_dev->chan_cnt; i++)
> +		kfree(swdma_dev->swdma_chans[i]);
> +
> +	kfree(swdma_dev->swdma_chans);
> +
> +	put_device(dma_dev->dev);
> +	kfree(swdma_dev);
> +}
> +
> +static int switchtec_dma_create(struct pci_dev *pdev)
> +{
> +	struct switchtec_dma_dev *swdma_dev;
> +	struct dma_device *dma;
> +	struct dma_chan *chan;
> +	int chan_cnt;
> +	int nr_vecs;
> +	int irq;
> +	int rc;
> +
> +	/*
> +	 * Create the switchtec dma device
> +	 */
> +	swdma_dev = kzalloc(sizeof(*swdma_dev), GFP_KERNEL);
> +	if (!swdma_dev)
> +		return -ENOMEM;
> +
> +	swdma_dev->bar = ioremap(pci_resource_start(pdev, 0),
> +				 pci_resource_len(pdev, 0));
> +
> +	pci_info(pdev, "Switchtec PSX/PFX DMA EP\n");
> +
> +	RCU_INIT_POINTER(swdma_dev->pdev, pdev);
> +
> +	nr_vecs = pci_msix_vec_count(pdev);
> +	rc = pci_alloc_irq_vectors(pdev, nr_vecs, nr_vecs, PCI_IRQ_MSIX);
> +	if (rc < 0)
> +		goto err_exit;
> +
> +	tasklet_init(&swdma_dev->chan_status_task,
> +		     switchtec_dma_chan_status_task,
> +		     (unsigned long)swdma_dev);
> +
> +	irq = readw(swdma_dev->bar + SWITCHTEC_REG_CHAN_STS_VEC);
> +	pci_dbg(pdev, "Channel pause irq vector %d\n", irq);
> +
> +	rc = pci_request_irq(pdev, irq, switchtec_dma_chan_status_isr, NULL,
> +			     swdma_dev, KBUILD_MODNAME);
> +	if (rc)
> +		goto err_exit;
> +
> +	swdma_dev->chan_status_irq = irq;
> +
> +	chan_cnt = readl(swdma_dev->bar + SWITCHTEC_REG_CHAN_CNT);
> +	if (!chan_cnt) {
> +		pci_err(pdev, "No channel configured.\n");
> +		rc = -ENXIO;
> +		goto err_exit;
> +	}
> +
> +	chan_cnt = switchtec_dma_chans_enumerate(swdma_dev, chan_cnt);
> +	if (chan_cnt < 0) {
> +		pci_err(pdev, "Failed to enumerate dma channels: %d\n",
> +			chan_cnt);
> +		rc = -ENXIO;
> +		goto err_exit;
> +	}
> +
> +	swdma_dev->chan_cnt = chan_cnt;
> +
> +	dma = &swdma_dev->dma_dev;
> +	dma->copy_align = DMAENGINE_ALIGN_1_BYTE;
> +	dma_cap_set(DMA_MEMCPY, dma->cap_mask);
> +	dma_cap_set(DMA_PRIVATE, dma->cap_mask);
> +	dma->dev = get_device(&pdev->dev);
> +
> +	dma->device_alloc_chan_resources = switchtec_dma_alloc_chan_resources;
> +	dma->device_free_chan_resources = switchtec_dma_free_chan_resources;
> +	dma->device_prep_dma_memcpy = switchtec_dma_prep_memcpy;
> +	dma->device_prep_dma_imm_data = switchtec_dma_prep_wimm_data;
> +	dma->device_issue_pending = switchtec_dma_issue_pending;
> +	dma->device_tx_status = switchtec_dma_tx_status;
> +	dma->device_pause = switchtec_dma_pause;
> +	dma->device_resume = switchtec_dma_resume;
> +	dma->device_terminate_all = switchtec_dma_terminate_all;
> +	dma->device_synchronize = switchtec_dma_synchronize;
> +	dma->device_release = switchtec_dma_release;
> +
> +	rc = dma_async_device_register(dma);
> +	if (rc) {
> +		pci_err(pdev, "Failed to register dma device: %d\n", rc);
> +		goto err_chans_release_exit;
> +	}
> +
> +	pci_info(pdev, "Channel count: %d\n", chan_cnt);

dev_info()?

> +
> +	list_for_each_entry(chan, &dma->channels, device_node)
> +		pci_info(pdev, "%s\n", dma_chan_name(chan));
> +
> +	pci_set_drvdata(pdev, swdma_dev);
> +
> +	return 0;
> +
> +err_chans_release_exit:
> +	switchtec_dma_chans_release(swdma_dev);
> +
> +err_exit:
> +	if (swdma_dev->chan_status_irq)
> +		free_irq(swdma_dev->chan_status_irq, swdma_dev);
> +
> +	iounmap(swdma_dev->bar);
> +	kfree(swdma_dev);
> +	return rc;
> +}
> +
> +static int switchtec_dma_probe(struct pci_dev *pdev,
> +			       const struct pci_device_id *id)
> +{
> +	int rc;
> +
> +	rc = pci_enable_device(pdev);
> +	if (rc)
> +		return rc;
> +
> +	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
> +	if (rc)
> +		goto err_disable;
> +
> +	rc = pci_request_mem_regions(pdev, KBUILD_MODNAME);
> +	if (rc)
> +		goto err_disable;
> +
> +	pci_set_master(pdev);
> +
> +	rc = switchtec_dma_create(pdev);
> +	if (rc)
> +		goto err_free;
> +
> +	pci_info(pdev, "Switchtec DMA Channels Registered\n");
> +
> +	return 0;
> +
> +err_free:
> +	pci_free_irq_vectors(pdev);
> +	pci_release_mem_regions(pdev);
> +
> +err_disable:
> +	pci_disable_device(pdev);
> +
> +	return rc;
> +}
> +
> +static void switchtec_dma_remove(struct pci_dev *pdev)
> +{
> +	struct switchtec_dma_dev *swdma_dev = pci_get_drvdata(pdev);
> +
> +	switchtec_dma_chans_release(swdma_dev);
> +
> +	tasklet_kill(&swdma_dev->chan_status_task);
> +
> +	rcu_assign_pointer(swdma_dev->pdev, NULL);
> +	synchronize_rcu();
> +
> +	pci_free_irq(pdev, swdma_dev->chan_status_irq, swdma_dev);
> +
> +	pci_free_irq_vectors(pdev);
> +
> +	dma_async_device_unregister(&swdma_dev->dma_dev);
> +
> +	iounmap(swdma_dev->bar);
> +	pci_release_mem_regions(pdev);
> +	pci_disable_device(pdev);
> +
> +	pci_info(pdev, "Switchtec DMA Channels Unregistered\n");
> +}
> +
> +/*
> + * Use vender/device and class to identify the DMA function.
> + */
> +#define SWITCHTEC_DMA_DEVICE(device_id) \
> +	{ \
> +		.vendor     = PCI_VENDOR_ID_MICROSEMI, \
> +		.device     = device_id, \
> +		.subvendor  = PCI_ANY_ID, \
> +		.subdevice  = PCI_ANY_ID, \
> +		.class      = PCI_CLASS_SYSTEM_OTHER << 8, \
> +		.class_mask = 0xFFFFFFFF, \
> +	}
> +
> +static const struct pci_device_id switchtec_dma_pci_tbl[] = {
> +	SWITCHTEC_DMA_DEVICE(0x4000), /* PFX 100XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4084), /* PFX 84XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4068), /* PFX 68XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4052), /* PFX 52XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4036), /* PFX 36XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4028), /* PFX 28XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4100), /* PSX 100XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4184), /* PSX 84XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4168), /* PSX 68XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4152), /* PSX 52XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4136), /* PSX 36XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4128), /* PSX 28XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4352), /* PFXA 52XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4336), /* PFXA 36XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4328), /* PFXA 28XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4452), /* PSXA 52XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4436), /* PSXA 36XG4 */
> +	SWITCHTEC_DMA_DEVICE(0x4428), /* PSXA 28XG4 */
> +	{0}
> +};
> +MODULE_DEVICE_TABLE(pci, switchtec_dma_pci_tbl);
> +
> +static struct pci_driver switchtec_dma_pci_driver = {
> +	.name           = KBUILD_MODNAME,
> +	.id_table       = switchtec_dma_pci_tbl,
> +	.probe          = switchtec_dma_probe,
> +	.remove		= switchtec_dma_remove,
> +};
> +module_pci_driver(switchtec_dma_pci_driver);
> -- 
> 2.25.1

Christoph Hellwig May 23, 2023, 6:01 a.m. UTC | #3

Hi Vinode,

I've tried to read your review, but as you're not trimming the
quoted text it was impossible to read.  Can you resend it following
proper mailing list ettiquette?

Kelvin Cao May 24, 2023, 4:58 p.m. UTC | #4

I trimmed the quote to make it easier to follow. I intentionally
skipped some style comments from Vinod in this reply. Hopefully I
didn't miss anything.


> > +#define SWITCHTEC_DMA_SQ_SIZE        SZ_32K
> > +#define SWITCHTEC_DMA_CQ_SIZE        SZ_32K
> > +
> > +#define SWITCHTEC_DMA_RING_SIZE      SWITCHTEC_DMA_SQ_SIZE
> > +
> > +static int wait_for_chan_status(struct chan_hw_regs __iomem
> > *chan_hw, u32 mask,
> > +             bool set)
> 
> single line would read much better! (here and few other places)
> 
> Also run checkpatch with --strict option, that will help catch style
> inconsistencies (i am seeing some below)

Ok.
> 
> > +{
> > +     u32 status;
> > +     int retry = 100;
> > +     int ret = -EIO;
> > +
> > +     do {
> > +             status = readl(&chan_hw->status);
> > +             if ((set && (status & mask)) ||
> > +                 (!set && !(status & mask))) {
> > +                     ret = 0;
> > +                     break;
> > +             }
> 
> why not use readl_poll_timeout()

Good point. Will use readl_poll_timeout_atomic().
> 
> > +
> > +static int disable_channel(struct switchtec_dma_chan *swdma_chan)
> > +{
> > +     u32 valid_en_se;
> > +     struct chan_fw_regs __iomem *chan_fw = swdma_chan-
> > >mmio_chan_fw;
> > +     struct pci_dev *pdev;
> > +
> > +     rcu_read_lock();
> > +     pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
> > +     if (!pdev) {
> > +             rcu_read_unlock();
> > +             return -ENODEV;
> > +     }
> > +
> > +     valid_en_se = readl(&chan_fw->valid_en_se);
> > +     valid_en_se &= ~SWITCHTEC_CHAN_ENABLE;
> > +
> > +     writel(valid_en_se, &chan_fw->valid_en_se);
> > +
> > +     rcu_read_unlock();
> > +     return 0;
> 
> only diff b/w enable/disable is bit ops, I guess we can have a common
> fn
> with argument for enable/disable

I'll make these two functions wrappers to another function which takes
enable/disable flag as parameter.
> 
> > +static struct dma_async_tx_descriptor
> > *switchtec_dma_prep_wimm_data(
> > +             struct dma_chan *c, dma_addr_t dma_dst, u64 data,
> > +             unsigned long flags)
> > +     __acquires(swdma_chan->submit_lock)
> > +{
> 
> can you please explain what is meant by wimm data and how it us used?

Sure. Generally it's just an implementation for the
device_prep_dma_imm_data() callback. I think it's an alternative method
to prep_mem and would be more convenient to use when the write is 8-
byte and the data to be moved is not in a DMA mapped memory location.
For example, we write to a doorbell register with the value from a
local variable which is not associated with a DMA address.
> 
> > 
> > +
> > +static dma_cookie_t switchtec_dma_tx_submit(
> > +             struct dma_async_tx_descriptor *desc)
> > +     __releases(swdma_chan->submit_lock)
> > +{
> > +     struct switchtec_dma_chan *swdma_chan =
> > +             to_switchtec_dma_chan(desc->chan);
> > +     dma_cookie_t cookie;
> > +
> > +     cookie = dma_cookie_assign(desc);
> > +
> > +     spin_unlock_bh(&swdma_chan->submit_lock);
> 
> I dont this is correct, why would you prevent users from preparing
> multiple descriptors..?


The driver implements the SQ with a pre-allocated buffer which means
the descriptor we are preparing has a determined slot in the queue
before we submitting it. To align with the way how cookies complete, I
have to make sure that the descriptors are prepared and submitted in
order. I think it's also the way some other DMA drivers work, like
ioat, plx. 
> 
> > +     size = SWITCHTEC_DMA_SQ_SIZE * sizeof(*swdma_chan->hw_sq);
> > +     swdma_chan->hw_sq = dma_alloc_coherent(swdma_dev-
> > >dma_dev.dev, size,
> > +                                            &swdma_chan-
> > >dma_addr_sq,
> > +                                            GFP_KERNEL);
> 
> this can be called from atomic context, GFP_NOWAIT pls

Sure.
> 
> > 
> > +     /* set sq/cq */
> > +     writel(lower_32_bits(swdma_chan->dma_addr_sq), &chan_fw-
> > >sq_base_lo);
> > +     writel(upper_32_bits(swdma_chan->dma_addr_sq), &chan_fw-
> > >sq_base_hi);
> > +     writel(lower_32_bits(swdma_chan->dma_addr_cq), &chan_fw-
> > >cq_base_lo);
> > +     writel(upper_32_bits(swdma_chan->dma_addr_cq), &chan_fw-
> > >cq_base_hi);
> > +
> > +     writew(SWITCHTEC_DMA_SQ_SIZE, &swdma_chan->mmio_chan_fw-
> > >sq_size);
> > +     writew(SWITCHTEC_DMA_CQ_SIZE, &swdma_chan->mmio_chan_fw-
> > >cq_size);
> 
> why is hardware being written in alloc call, the job is to prepare
> descritor, hw write should happen when we submit the descriptors..

The descriptors in the queue are pre-allocated so I think it's proper
to convey the info to hardware at this point. And in submit only the
cookie is assigned. 
> 
> > +     rc = dma_async_device_register(dma);
> > +     if (rc) {
> > +             pci_err(pdev, "Failed to register dma device: %d\n",
> > rc);
> > +             goto err_chans_release_exit;
> > +     }
> > +
> > +     pci_info(pdev, "Channel count: %d\n", chan_cnt);
> 
> dev_info()?

Any specific reason for switching to dev_info()?  


Thanks,
Kelvin

Christoph Hellwig July 24, 2023, 4:32 p.m. UTC | #5

Kelvin, can you resend an updated version so that we can finally
get the driver merged for 6.6?

Kelvin Cao July 24, 2023, 11:54 p.m. UTC | #6

On Mon, 2023-07-24 at 09:32 -0700, Christoph Hellwig wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> Kelvin, can you resend an updated version so that we can finally
> get the driver merged for 6.6?
> 

Christoph, I was waiting for Vinod's comment on the last review. And
it's been a while. So yes, I'll resend the updated version and maybe
it's another way to resume the review.

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index e0ad886d3163..24e8d4463592 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20346,6 +20346,12 @@  S:	Supported
 F:	include/net/switchdev.h
 F:	net/switchdev/
 
+SWITCHTEC DMA DRIVER
+M:	Kelvin Cao <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	drivers/dma/switchtec_dma.c
+
 SY8106A REGULATOR DRIVER
 M:	Icenowy Zheng <[e-mail]>
 S:	Maintained
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index f5f422f9b850..cfc8b1988a3b 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -610,6 +610,15 @@  config SPRD_DMA
 	help
 	  Enable support for the on-chip DMA controller on Spreadtrum platform.
 
+config SWITCHTEC_DMA
+	tristate "Switchtec PSX/PFX Switch DMA Engine Support"
+	depends on PCI
+	select DMA_ENGINE
+	help
+	  Some Switchtec PSX/PFX PCIe Switches support additional DMA engines.
+	  These are exposed via an extra function on the switch's upstream
+	  port.
+
 config TXX9_DMAC
 	tristate "Toshiba TXx9 SoC DMA support"
 	depends on MACH_TX49XX
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index a4fd1ce29510..977c97cda53d 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -70,6 +70,7 @@  obj-$(CONFIG_STM32_DMA) += stm32-dma.o
 obj-$(CONFIG_STM32_DMAMUX) += stm32-dmamux.o
 obj-$(CONFIG_STM32_MDMA) += stm32-mdma.o
 obj-$(CONFIG_SPRD_DMA) += sprd-dma.o
+obj-$(CONFIG_SWITCHTEC_DMA) += switchtec_dma.o
 obj-$(CONFIG_TXX9_DMAC) += txx9dmac.o
 obj-$(CONFIG_TEGRA186_GPC_DMA) += tegra186-gpc-dma.o
 obj-$(CONFIG_TEGRA20_APB_DMA) += tegra20-apb-dma.o
diff --git a/drivers/dma/switchtec_dma.c b/drivers/dma/switchtec_dma.c
new file mode 100644
index 000000000000..2df6ad5c3ce6
--- /dev/null
+++ b/drivers/dma/switchtec_dma.c
@@ -0,0 +1,1570 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Microchip Switchtec(tm) DMA Controller Driver
+ * Copyright (c) 2023, Kelvin Cao <[e-mail]>
+ * Copyright (c) 2023, Microchip Corporation
+ */
+
+#include <linux/circ_buf.h>
+#include <linux/dmaengine.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/delay.h>
+
+#include "dmaengine.h"
+
+MODULE_DESCRIPTION("Switchtec PCIe Switch DMA Engine");
+MODULE_VERSION("0.1");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Kelvin Cao");
+
+#define	SWITCHTEC_DMAC_CHAN_CTRL_OFFSET		0x1000
+#define	SWITCHTEC_DMAC_CHAN_CFG_STS_OFFSET	0x160000
+
+#define SWITCHTEC_DMA_CHAN_HW_REGS_SIZE		0x1000
+#define SWITCHTEC_DMA_CHAN_FW_REGS_SIZE		0x80
+
+#define SWITCHTEC_REG_CAP		0x80
+#define SWITCHTEC_REG_CHAN_CNT		0x84
+#define SWITCHTEC_REG_TAG_LIMIT		0x90
+#define SWITCHTEC_REG_CHAN_STS_VEC	0x94
+#define SWITCHTEC_REG_SE_BUF_CNT	0x98
+#define SWITCHTEC_REG_SE_BUF_BASE	0x9a
+
+#define SWITCHTEC_DESC_MAX_SIZE		0x100000
+
+#define SWITCHTEC_CHAN_CTRL_PAUSE	BIT(0)
+#define SWITCHTEC_CHAN_CTRL_HALT	BIT(1)
+#define SWITCHTEC_CHAN_CTRL_RESET	BIT(2)
+#define SWITCHTEC_CHAN_CTRL_ERR_PAUSE	BIT(3)
+
+#define SWITCHTEC_CHAN_STS_PAUSED	BIT(9)
+#define SWITCHTEC_CHAN_STS_HALTED	BIT(10)
+#define SWITCHTEC_CHAN_STS_PAUSED_MASK	GENMASK(29, 13)
+
+static const char * const channel_status_str[] = {
+	[13] = "received a VDM with length error status",
+	[14] = "received a VDM or Cpl with Unsupported Request error status",
+	[15] = "received a VDM or Cpl with Completion Abort error status",
+	[16] = "received a VDM with ECRC error status",
+	[17] = "received a VDM with EP error status",
+	[18] = "received a VDM with Reserved Cpl error status",
+	[19] = "received only part of split SE CplD",
+	[20] = "the ISP_DMAC detected a Completion Time Out",
+	[21] = "received a Cpl with Unsupported Request status",
+	[22] = "received a Cpl with Completion Abort status",
+	[23] = "received a Cpl with a reserved status",
+	[24] = "received a TLP with ECRC error status in its metadata",
+	[25] = "received a TLP with the EP bit set in the header",
+	[26] = "the ISP_DMAC tried to process a SE with an invalid Connection ID",
+	[27] = "the ISP_DMAC tried to process a SE with an invalid Remote Host interrupt",
+	[28] = "a reserved opcode was detected in an SE",
+	[29] = "received a SE Cpl with error status",
+};
+
+struct chan_hw_regs {
+	u16 cq_head;
+	u16 rsvd1;
+	u16 sq_tail;
+	u16 rsvd2;
+	u8 ctrl;
+	u8 rsvd3[3];
+	u16 status;
+	u16 rsvd4;
+};
+
+enum {
+	PERF_BURST_SCALE = 0x1,
+	PERF_BURST_SIZE = 0x6,
+	PERF_INTERVAL = 0x0,
+	PERF_MRRS = 0x3,
+	PERF_ARB_WEIGHT = 0x1,
+};
+
+enum {
+	PERF_BURST_SCALE_SHIFT = 0x2,
+	PERF_BURST_SCALE_MASK = 0x3,
+	PERF_MRRS_SHIFT = 0x4,
+	PERF_MRRS_MASK = 0x7,
+	PERF_INTERVAL_SHIFT = 0x8,
+	PERF_INTERVAL_MASK = 0x7,
+	PERF_BURST_SIZE_SHIFT = 0xc,
+	PERF_BURST_SIZE_MASK = 0x7,
+	PERF_ARB_WEIGHT_SHIFT = 0x18,
+	PERF_ARB_WEIGHT_MASK = 0xff,
+};
+
+enum {
+	PERF_MIN_INTERVAL = 0,
+	PERF_MAX_INTERVAL = 0x7,
+	PERF_MIN_BURST_SIZE = 0,
+	PERF_MAX_BURST_SIZE = 0x7,
+	PERF_MIN_BURST_SCALE = 0,
+	PERF_MAX_BURST_SCALE = 0x2,
+	PERF_MIN_MRRS = 0,
+	PERF_MAX_MRRS = 0x7,
+};
+
+enum {
+	SE_BUF_BASE_SHIFT = 0x2,
+	SE_BUF_BASE_MASK = 0x1ff,
+	SE_BUF_LEN_SHIFT = 0xc,
+	SE_BUF_LEN_MASK = 0x1ff,
+	SE_THRESH_SHIFT = 0x17,
+	SE_THRESH_MASK = 0x1ff,
+};
+
+#define SWITCHTEC_CHAN_ENABLE	BIT(1)
+
+struct chan_fw_regs {
+	u32 valid_en_se;
+	u32 cq_base_lo;
+	u32 cq_base_hi;
+	u16 cq_size;
+	u16 rsvd1;
+	u32 sq_base_lo;
+	u32 sq_base_hi;
+	u16 sq_size;
+	u16 rsvd2;
+	u32 int_vec;
+	u32 perf_cfg;
+	u32 rsvd3;
+	u32 perf_latency_selector;
+	u32 perf_fetched_se_cnt_lo;
+	u32 perf_fetched_se_cnt_hi;
+	u32 perf_byte_cnt_lo;
+	u32 perf_byte_cnt_hi;
+	u32 rsvd4;
+	u16 perf_se_pending;
+	u16 perf_se_buf_empty;
+	u32 perf_chan_idle;
+	u32 perf_lat_max;
+	u32 perf_lat_min;
+	u32 perf_lat_last;
+	u16 sq_current;
+	u16 sq_phase;
+	u16 cq_current;
+	u16 cq_phase;
+};
+
+enum cmd {
+	CMD_GET_HOST_LIST = 1,
+	CMD_REGISTER_BUF = 2,
+	CMD_UNREGISTER_BUF = 3,
+	CMD_GET_BUF_LIST = 4,
+	CMD_GET_OWN_BUF_LIST = 5,
+};
+
+enum cmd_status {
+	CMD_STATUS_IDLE = 0,
+	CMD_STATUS_INPROGRESS = 0x1,
+	CMD_STATUS_DONE = 0x2,
+	CMD_STATUS_ERROR = 0xFF,
+};
+
+struct switchtec_dma_chan {
+	struct switchtec_dma_dev *swdma_dev;
+	struct dma_chan dma_chan;
+	struct chan_hw_regs __iomem *mmio_chan_hw;
+	struct chan_fw_regs __iomem *mmio_chan_fw;
+	spinlock_t hw_ctrl_lock;
+
+	struct tasklet_struct desc_task;
+	spinlock_t submit_lock;
+	bool ring_active;
+	int cid;
+	spinlock_t complete_lock;
+	bool comp_ring_active;
+
+	/* channel index and irq */
+	int index;
+	int irq;
+
+	/*
+	 * In driver context, head is advanced by producer while
+	 * tail is advanced by consumer.
+	 */
+
+	/* the head and tail for both desc_ring and hw_sq */
+	int head;
+	int tail;
+	int phase_tag;
+	struct switchtec_dma_desc **desc_ring;
+	struct switchtec_dma_hw_se_desc *hw_sq;
+	dma_addr_t dma_addr_sq;
+
+	/* the tail for hw_cq */
+	int cq_tail;
+	struct switchtec_dma_hw_ce *hw_cq;
+	dma_addr_t dma_addr_cq;
+
+	struct list_head list;
+};
+
+struct switchtec_dma_dev {
+	struct dma_device dma_dev;
+	struct pci_dev __rcu *pdev;
+	struct switchtec_dma_chan **swdma_chans;
+	int chan_cnt;
+	int chan_status_irq;
+	void __iomem *bar;
+	struct tasklet_struct chan_status_task;
+};
+
+static struct switchtec_dma_chan *to_switchtec_dma_chan(struct dma_chan *c)
+{
+	return container_of(c, struct switchtec_dma_chan, dma_chan);
+}
+
+static struct device *to_chan_dev(struct switchtec_dma_chan *swdma_chan)
+{
+	return &swdma_chan->dma_chan.dev->device;
+}
+
+enum switchtec_dma_opcode {
+	SWITCHTEC_DMA_OPC_MEMCPY = 0,
+	SWITCHTEC_DMA_OPC_RDIMM = 0x1,
+	SWITCHTEC_DMA_OPC_WRIMM = 0x2,
+	SWITCHTEC_DMA_OPC_RHI = 0x6,
+	SWITCHTEC_DMA_OPC_NOP = 0x7,
+};
+
+struct switchtec_dma_hw_se_desc {
+	u8 opc;
+	u8 ctrl;
+	__le16 tlp_setting;
+	__le16 rsvd1;
+	__le16 cid;
+	__le32 byte_cnt;
+	__le32 addr_lo; /* SADDR_LO/WIADDR_LO */
+	__le32 addr_hi; /* SADDR_HI/WIADDR_HI */
+	__le32 daddr_lo;
+	__le32 daddr_hi;
+	__le16 dfid;
+	__le16 sfid;
+};
+
+#define SWITCHTEC_SE_DFM		BIT(5)
+#define SWITCHTEC_SE_LIOF		BIT(6)
+#define SWITCHTEC_SE_BRR		BIT(7)
+#define SWITCHTEC_SE_CID_MASK		GENMASK(15, 0)
+
+#define SWITCHTEC_CE_SC_LEN_ERR		BIT(0)
+#define SWITCHTEC_CE_SC_UR		BIT(1)
+#define SWITCHTEC_CE_SC_CA		BIT(2)
+#define SWITCHTEC_CE_SC_RSVD_CPL	BIT(3)
+#define SWITCHTEC_CE_SC_ECRC_ERR	BIT(4)
+#define SWITCHTEC_CE_SC_EP_SET		BIT(5)
+#define SWITCHTEC_CE_SC_D_RD_CTO	BIT(8)
+#define SWITCHTEC_CE_SC_D_RIMM_UR	BIT(9)
+#define SWITCHTEC_CE_SC_D_RIMM_CA	BIT(10)
+#define SWITCHTEC_CE_SC_D_RIMM_RSVD_CPL	BIT(11)
+#define SWITCHTEC_CE_SC_D_ECRC		BIT(12)
+#define SWITCHTEC_CE_SC_D_EP_SET	BIT(13)
+#define SWITCHTEC_CE_SC_D_BAD_CONNID	BIT(14)
+#define SWITCHTEC_CE_SC_D_BAD_RHI_ADDR	BIT(15)
+#define SWITCHTEC_CE_SC_D_INVD_CMD	BIT(16)
+#define SWITCHTEC_CE_SC_MASK		GENMASK(16, 0)
+
+struct switchtec_dma_hw_ce {
+	__le32 rdimm_cpl_dw0;
+	__le32 rdimm_cpl_dw1;
+	__le32 rsvd1;
+	__le32 cpl_byte_cnt;
+	__le16 sq_head;
+	__le16 rsvd2;
+	__le32 rsvd3;
+	__le32 sts_code;
+	__le16 cid;
+	__le16 phase_tag;
+};
+
+struct switchtec_dma_desc {
+	struct dma_async_tx_descriptor txd;
+	struct switchtec_dma_hw_se_desc *hw;
+	u32 orig_size;
+	bool completed;
+};
+
+#define SWITCHTEC_INVALID_HFID 0xffff
+
+enum desc_type {
+	MEMCPY,
+	WIMM,
+	UNKNOWN_TRANSACTION,
+};
+
+#define SWITCHTEC_DMA_SQ_SIZE	SZ_32K
+#define SWITCHTEC_DMA_CQ_SIZE	SZ_32K
+
+#define SWITCHTEC_DMA_RING_SIZE	SWITCHTEC_DMA_SQ_SIZE
+
+static int wait_for_chan_status(struct chan_hw_regs __iomem *chan_hw, u32 mask,
+		bool set)
+{
+	u32 status;
+	int retry = 100;
+	int ret = -EIO;
+
+	do {
+		status = readl(&chan_hw->status);
+		if ((set && (status & mask)) ||
+		    (!set && !(status & mask))) {
+			ret = 0;
+			break;
+		}
+
+		udelay(1000);
+	} while (retry--);
+
+	return ret;
+}
+
+static int halt_channel(struct switchtec_dma_chan *swdma_chan)
+{
+	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
+	struct pci_dev *pdev;
+	int ret;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		ret = -ENODEV;
+		goto unlock_and_exit;
+	}
+
+	spin_lock(&swdma_chan->hw_ctrl_lock);
+	writeb(SWITCHTEC_CHAN_CTRL_HALT, &chan_hw->ctrl);
+	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_HALTED, true);
+	spin_unlock(&swdma_chan->hw_ctrl_lock);
+
+unlock_and_exit:
+	rcu_read_unlock();
+	return ret;
+}
+
+static int unhalt_channel(struct switchtec_dma_chan *swdma_chan)
+{
+	u8 ctrl;
+	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
+	struct pci_dev *pdev;
+	int ret;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		ret = -ENODEV;
+		goto unlock_and_exit;
+	}
+
+	spin_lock(&swdma_chan->hw_ctrl_lock);
+	ctrl = readb(&chan_hw->ctrl);
+	ctrl &= ~SWITCHTEC_CHAN_CTRL_HALT;
+	writeb(ctrl, &chan_hw->ctrl);
+	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_HALTED, false);
+	spin_unlock(&swdma_chan->hw_ctrl_lock);
+
+unlock_and_exit:
+	rcu_read_unlock();
+	return ret;
+}
+
+static void flush_pci_write(struct chan_hw_regs __iomem *chan_hw)
+{
+	readl(&chan_hw->cq_head);
+}
+
+static int reset_channel(struct switchtec_dma_chan *swdma_chan)
+{
+	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
+	struct pci_dev *pdev;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		rcu_read_unlock();
+		return -ENODEV;
+	}
+
+	spin_lock(&swdma_chan->hw_ctrl_lock);
+	writel(SWITCHTEC_CHAN_CTRL_RESET | SWITCHTEC_CHAN_CTRL_ERR_PAUSE,
+	       &chan_hw->ctrl);
+	flush_pci_write(chan_hw);
+
+	udelay(1000);
+
+	writel(SWITCHTEC_CHAN_CTRL_ERR_PAUSE, &chan_hw->ctrl);
+	spin_unlock(&swdma_chan->hw_ctrl_lock);
+	flush_pci_write(chan_hw);
+
+	rcu_read_unlock();
+	return 0;
+}
+
+static int pause_reset_channel(struct switchtec_dma_chan *swdma_chan)
+{
+	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
+	struct pci_dev *pdev;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		rcu_read_unlock();
+		return -ENODEV;
+	}
+
+	spin_lock(&swdma_chan->hw_ctrl_lock);
+	writeb(SWITCHTEC_CHAN_CTRL_PAUSE, &chan_hw->ctrl);
+	spin_unlock(&swdma_chan->hw_ctrl_lock);
+
+	flush_pci_write(chan_hw);
+
+	rcu_read_unlock();
+
+	/* wait 60ms to ensure no pending CEs */
+	mdelay(60);
+
+	return reset_channel(swdma_chan);
+
+}
+
+static int switchtec_dma_pause(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
+	struct pci_dev *pdev;
+	int ret;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		ret = -ENODEV;
+		goto unlock_and_exit;
+	}
+
+	spin_lock(&swdma_chan->hw_ctrl_lock);
+	writeb(SWITCHTEC_CHAN_CTRL_PAUSE, &chan_hw->ctrl);
+	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_PAUSED, true);
+	spin_unlock(&swdma_chan->hw_ctrl_lock);
+
+unlock_and_exit:
+	rcu_read_unlock();
+	return ret;
+}
+
+static int switchtec_dma_resume(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+	struct chan_hw_regs __iomem *chan_hw = swdma_chan->mmio_chan_hw;
+	struct pci_dev *pdev;
+	int ret;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		ret = -ENODEV;
+		goto unlock_and_exit;
+	}
+
+	spin_lock(&swdma_chan->hw_ctrl_lock);
+	writeb(0, &chan_hw->ctrl);
+	ret = wait_for_chan_status(chan_hw, SWITCHTEC_CHAN_STS_PAUSED, false);
+	spin_unlock(&swdma_chan->hw_ctrl_lock);
+
+unlock_and_exit:
+	rcu_read_unlock();
+	return ret;
+}
+
+static int enable_channel(struct switchtec_dma_chan *swdma_chan)
+{
+	u32 valid_en_se;
+	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
+	struct pci_dev *pdev;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		rcu_read_unlock();
+		return -ENODEV;
+	}
+
+	valid_en_se = readl(&chan_fw->valid_en_se);
+	valid_en_se |= SWITCHTEC_CHAN_ENABLE;
+
+	writel(valid_en_se, &chan_fw->valid_en_se);
+
+	rcu_read_unlock();
+	return 0;
+}
+
+static int disable_channel(struct switchtec_dma_chan *swdma_chan)
+{
+	u32 valid_en_se;
+	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
+	struct pci_dev *pdev;
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+	if (!pdev) {
+		rcu_read_unlock();
+		return -ENODEV;
+	}
+
+	valid_en_se = readl(&chan_fw->valid_en_se);
+	valid_en_se &= ~SWITCHTEC_CHAN_ENABLE;
+
+	writel(valid_en_se, &chan_fw->valid_en_se);
+
+	rcu_read_unlock();
+	return 0;
+}
+
+static struct switchtec_dma_desc *switchtec_dma_get_desc(
+		struct switchtec_dma_chan *swdma_chan, int i)
+{
+	return swdma_chan->desc_ring[i];
+}
+
+static struct switchtec_dma_hw_ce *switchtec_dma_get_ce(
+		struct switchtec_dma_chan *swdma_chan, int i)
+{
+	return &swdma_chan->hw_cq[i];
+}
+
+static void switchtec_dma_process_desc(struct switchtec_dma_chan *swdma_chan)
+{
+	struct device *chan_dev = to_chan_dev(swdma_chan);
+	struct dmaengine_result res;
+	struct switchtec_dma_desc *desc;
+	struct switchtec_dma_hw_ce *ce;
+	__le16 phase_tag;
+	int tail;
+	int cid;
+	int se_idx;
+	u32 sts_code;
+	int i;
+	__le32 *p;
+
+	do {
+		spin_lock_bh(&swdma_chan->complete_lock);
+		if (!swdma_chan->comp_ring_active) {
+			spin_unlock_bh(&swdma_chan->complete_lock);
+			break;
+		}
+
+		ce = switchtec_dma_get_ce(swdma_chan, swdma_chan->cq_tail);
+
+		/*
+		 * phase_tag is updated by hardware, ensure the value is
+		 * not from the cache
+		 */
+		phase_tag = smp_load_acquire(&ce->phase_tag);
+		if (le16_to_cpu(phase_tag) == swdma_chan->phase_tag) {
+			spin_unlock_bh(&swdma_chan->complete_lock);
+			break;
+		}
+
+		cid = le16_to_cpu(ce->cid);
+		se_idx = cid & (SWITCHTEC_DMA_SQ_SIZE - 1);
+		desc = switchtec_dma_get_desc(swdma_chan, se_idx);
+
+		tail = swdma_chan->tail;
+
+		res.residue = desc->orig_size - le32_to_cpu(ce->cpl_byte_cnt);
+
+		sts_code = le32_to_cpu(ce->sts_code);
+
+		if (!(sts_code & SWITCHTEC_CE_SC_MASK)) {
+			res.result = DMA_TRANS_NOERROR;
+		} else {
+			if (sts_code & SWITCHTEC_CE_SC_D_RD_CTO)
+				res.result = DMA_TRANS_READ_FAILED;
+			else
+				res.result = DMA_TRANS_WRITE_FAILED;
+
+			dev_err(chan_dev, "CID 0x%04x failed, SC 0x%08x\n", cid,
+				(u32)(sts_code & SWITCHTEC_CE_SC_MASK));
+
+			p = (__le32 *)ce;
+			for (i = 0; i < sizeof(*ce)/4; i++) {
+				dev_err(chan_dev, "CE DW%d: 0x%08x\n", i,
+					le32_to_cpu(*p));
+				p++;
+			}
+		}
+
+		desc->completed = true;
+
+		swdma_chan->cq_tail++;
+		swdma_chan->cq_tail &= SWITCHTEC_DMA_CQ_SIZE - 1;
+
+		rcu_read_lock();
+		if (!rcu_dereference(swdma_chan->swdma_dev->pdev)) {
+			rcu_read_unlock();
+			spin_unlock_bh(&swdma_chan->complete_lock);
+			return;
+		}
+		writew(swdma_chan->cq_tail, &swdma_chan->mmio_chan_hw->cq_head);
+		rcu_read_unlock();
+
+		if (swdma_chan->cq_tail == 0)
+			swdma_chan->phase_tag = !swdma_chan->phase_tag;
+
+		/*  Out of order CE */
+		if (se_idx != tail) {
+			spin_unlock_bh(&swdma_chan->complete_lock);
+			continue;
+		}
+
+		do {
+			dma_cookie_complete(&desc->txd);
+			dma_descriptor_unmap(&desc->txd);
+			dmaengine_desc_get_callback_invoke(&desc->txd, &res);
+			desc->txd.callback = NULL;
+			desc->txd.callback_result = NULL;
+			desc->completed = false;
+
+			tail++;
+			tail &= SWITCHTEC_DMA_SQ_SIZE - 1;
+
+			/*
+			 * Ensure the desc updates are visible before updating
+			 * the tail index
+			 */
+			smp_store_release(&swdma_chan->tail, tail);
+			desc = switchtec_dma_get_desc(swdma_chan,
+						      swdma_chan->tail);
+			if (!desc->completed)
+				break;
+		} while (CIRC_CNT(READ_ONCE(swdma_chan->head), swdma_chan->tail,
+				  SWITCHTEC_DMA_SQ_SIZE));
+
+		spin_unlock_bh(&swdma_chan->complete_lock);
+	} while (1);
+}
+
+static void switchtec_dma_abort_desc(struct switchtec_dma_chan *swdma_chan,
+		int force)
+{
+	struct dmaengine_result res;
+	struct switchtec_dma_desc *desc;
+
+	if (!force)
+		switchtec_dma_process_desc(swdma_chan);
+
+	spin_lock_bh(&swdma_chan->complete_lock);
+
+	while (CIRC_CNT(swdma_chan->head, swdma_chan->tail,
+			SWITCHTEC_DMA_SQ_SIZE) >= 1) {
+		desc = switchtec_dma_get_desc(swdma_chan, swdma_chan->tail);
+
+		res.residue = desc->orig_size;
+		res.result = DMA_TRANS_ABORTED;
+
+		dma_cookie_complete(&desc->txd);
+		dma_descriptor_unmap(&desc->txd);
+		if (!force)
+			dmaengine_desc_get_callback_invoke(&desc->txd, &res);
+		desc->txd.callback = NULL;
+		desc->txd.callback_result = NULL;
+
+		swdma_chan->tail++;
+		swdma_chan->tail &= SWITCHTEC_DMA_SQ_SIZE - 1;
+	}
+
+	spin_unlock_bh(&swdma_chan->complete_lock);
+}
+
+static void switchtec_dma_chan_stop(struct switchtec_dma_chan *swdma_chan)
+{
+	int rc;
+
+	rc = halt_channel(swdma_chan);
+	if (rc)
+		return;
+
+	rcu_read_lock();
+	if (!rcu_dereference(swdma_chan->swdma_dev->pdev)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	writel(0, &swdma_chan->mmio_chan_fw->sq_base_lo);
+	writel(0, &swdma_chan->mmio_chan_fw->sq_base_hi);
+	writel(0, &swdma_chan->mmio_chan_fw->cq_base_lo);
+	writel(0, &swdma_chan->mmio_chan_fw->cq_base_hi);
+
+	rcu_read_unlock();
+}
+
+static int switchtec_dma_terminate_all(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+
+	spin_lock_bh(&swdma_chan->complete_lock);
+	swdma_chan->comp_ring_active = false;
+	spin_unlock_bh(&swdma_chan->complete_lock);
+
+	return pause_reset_channel(swdma_chan);
+}
+
+static void switchtec_dma_synchronize(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+	int rc;
+
+	switchtec_dma_abort_desc(swdma_chan, 1);
+
+	rc = enable_channel(swdma_chan);
+	if (rc)
+		return;
+
+	rc = reset_channel(swdma_chan);
+	if (rc)
+		return;
+
+	rc = unhalt_channel(swdma_chan);
+	if (rc)
+		return;
+
+	spin_lock_bh(&swdma_chan->submit_lock);
+	swdma_chan->head = 0;
+	spin_unlock_bh(&swdma_chan->submit_lock);
+
+	spin_lock_bh(&swdma_chan->complete_lock);
+	swdma_chan->comp_ring_active = true;
+	swdma_chan->phase_tag = 0;
+	swdma_chan->tail = 0;
+	swdma_chan->cq_tail = 0;
+	swdma_chan->cid = 0;
+	dma_cookie_init(chan);
+	spin_unlock_bh(&swdma_chan->complete_lock);
+}
+
+static void switchtec_dma_desc_task(unsigned long data)
+{
+	struct switchtec_dma_chan *swdma_chan = (void *)data;
+
+	switchtec_dma_process_desc(swdma_chan);
+}
+
+static void switchtec_dma_chan_status_task(unsigned long data)
+{
+	struct switchtec_dma_dev *swdma_dev = (void *)data;
+	struct dma_device *dma_dev = &swdma_dev->dma_dev;
+	struct dma_chan *chan;
+	struct switchtec_dma_chan *swdma_chan;
+	struct chan_hw_regs __iomem *chan_hw;
+	struct device *chan_dev;
+	u32 chan_status;
+	int bit;
+
+	list_for_each_entry(chan, &dma_dev->channels, device_node) {
+		swdma_chan = to_switchtec_dma_chan(chan);
+		chan_dev = to_chan_dev(swdma_chan);
+		chan_hw = swdma_chan->mmio_chan_hw;
+
+		rcu_read_lock();
+		if (!rcu_dereference(swdma_dev->pdev)) {
+			rcu_read_unlock();
+			return;
+		}
+
+		chan_status = readl(&chan_hw->status);
+		chan_status &= SWITCHTEC_CHAN_STS_PAUSED_MASK;
+		rcu_read_unlock();
+
+		bit = ffs(chan_status);
+		if (!bit)
+			dev_dbg(chan_dev, "No pause bit set.");
+		else
+			dev_err(chan_dev, "Paused, %s\n",
+				channel_status_str[bit - 1]);
+	}
+}
+
+static struct dma_async_tx_descriptor *switchtec_dma_prep_desc(
+		struct dma_chan *c, enum desc_type type, u16 dst_fid,
+		dma_addr_t dma_dst, u16 src_fid, dma_addr_t dma_src, u64 data,
+		size_t len, unsigned long flags)
+	__acquires(swdma_chan->submit_lock)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(c);
+	struct switchtec_dma_desc *desc;
+	int head;
+	int tail;
+
+
+	if (type != MEMCPY && type != WIMM) {
+		/*
+		 * Keep sparse happy by restoring an even lock count on
+		 * this lock.
+		 */
+		__acquire(swdma_chan->submit_lock);
+		return NULL;
+	}
+
+	spin_lock_bh(&swdma_chan->submit_lock);
+
+	if (!swdma_chan->ring_active)
+		goto err_unlock;
+
+	tail = READ_ONCE(swdma_chan->tail);
+	head = swdma_chan->head;
+
+	if (!CIRC_SPACE(head, tail, SWITCHTEC_DMA_RING_SIZE))
+		goto err_unlock;
+
+	desc = switchtec_dma_get_desc(swdma_chan, head);
+
+	if (src_fid != SWITCHTEC_INVALID_HFID &&
+	    dst_fid != SWITCHTEC_INVALID_HFID)
+		desc->hw->ctrl |= SWITCHTEC_SE_DFM;
+
+	if (flags & DMA_PREP_INTERRUPT)
+		desc->hw->ctrl |= SWITCHTEC_SE_LIOF;
+
+	if (flags & DMA_PREP_FENCE)
+		desc->hw->ctrl |= SWITCHTEC_SE_BRR;
+
+	desc->txd.flags = flags;
+
+	desc->completed = false;
+	if (type == MEMCPY) {
+		desc->hw->opc = SWITCHTEC_DMA_OPC_MEMCPY;
+		desc->hw->addr_lo = cpu_to_le32(lower_32_bits(dma_src));
+		desc->hw->addr_hi = cpu_to_le32(upper_32_bits(dma_src));
+	} else {
+		desc->hw->opc = SWITCHTEC_DMA_OPC_WRIMM;
+		desc->hw->addr_lo = cpu_to_le32(lower_32_bits(data));
+		desc->hw->addr_hi = cpu_to_le32(upper_32_bits(data));
+	}
+	desc->hw->daddr_lo = cpu_to_le32(lower_32_bits(dma_dst));
+	desc->hw->daddr_hi = cpu_to_le32(upper_32_bits(dma_dst));
+	desc->hw->byte_cnt = cpu_to_le32(len);
+	desc->hw->tlp_setting = 0;
+	desc->hw->dfid = cpu_to_le16(dst_fid);
+	desc->hw->sfid = cpu_to_le16(src_fid);
+	swdma_chan->cid &= SWITCHTEC_SE_CID_MASK;
+	desc->hw->cid = cpu_to_le16(swdma_chan->cid++);
+	desc->orig_size = len;
+
+	head++;
+	head &= SWITCHTEC_DMA_RING_SIZE - 1;
+
+	/*
+	 * Ensure the desc updates are visible before updating the head index
+	 */
+	smp_store_release(&swdma_chan->head, head);
+
+	/* return with the lock held, it will be released in tx_submit */
+
+	return &desc->txd;
+
+err_unlock:
+	/*
+	 * Keep sparse happy by restoring an even lock count on
+	 * this lock.
+	 */
+	__acquire(swdma_chan->submit_lock);
+
+	spin_unlock_bh(&swdma_chan->submit_lock);
+	return NULL;
+}
+
+static struct dma_async_tx_descriptor *switchtec_dma_prep_memcpy(
+		struct dma_chan *c, dma_addr_t dma_dst, dma_addr_t dma_src,
+		size_t len, unsigned long flags)
+	__acquires(swdma_chan->submit_lock)
+{
+	if (len > SWITCHTEC_DESC_MAX_SIZE) {
+		/*
+		 * Keep sparse happy by restoring an even lock count on
+		 * this lock.
+		 */
+		__acquire(swdma_chan->submit_lock);
+		return NULL;
+	}
+
+	return switchtec_dma_prep_desc(c, MEMCPY, SWITCHTEC_INVALID_HFID,
+				       dma_dst, SWITCHTEC_INVALID_HFID, dma_src,
+				       0, len, flags);
+}
+
+static struct dma_async_tx_descriptor *switchtec_dma_prep_wimm_data(
+		struct dma_chan *c, dma_addr_t dma_dst, u64 data,
+		unsigned long flags)
+	__acquires(swdma_chan->submit_lock)
+{
+	size_t len = sizeof(data);
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(c);
+	struct device *chan_dev = to_chan_dev(swdma_chan);
+
+	if ((len == 8) && (dma_dst & ((1 << DMAENGINE_ALIGN_8_BYTES) - 1))) {
+		dev_err(chan_dev,
+			"QW WIMM dst addr 0x%08x_%08x not QW aligned!\n",
+			upper_32_bits(dma_dst), lower_32_bits(dma_dst));
+		/*
+		 * Keep sparse happy by restoring an even lock count on
+		 * this lock.
+		 */
+		__acquire(swdma_chan->submit_lock);
+		return NULL;
+	}
+
+	return switchtec_dma_prep_desc(c, WIMM, SWITCHTEC_INVALID_HFID, dma_dst,
+				       SWITCHTEC_INVALID_HFID, 0, data, len,
+				       flags);
+}
+
+static dma_cookie_t switchtec_dma_tx_submit(
+		struct dma_async_tx_descriptor *desc)
+	__releases(swdma_chan->submit_lock)
+{
+	struct switchtec_dma_chan *swdma_chan =
+		to_switchtec_dma_chan(desc->chan);
+	dma_cookie_t cookie;
+
+	cookie = dma_cookie_assign(desc);
+
+	spin_unlock_bh(&swdma_chan->submit_lock);
+
+	return cookie;
+}
+
+static enum dma_status switchtec_dma_tx_status(struct dma_chan *chan,
+		dma_cookie_t cookie, struct dma_tx_state *txstate)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+	enum dma_status ret;
+
+	ret = dma_cookie_status(chan, cookie, txstate);
+	if (ret == DMA_COMPLETE)
+		return ret;
+
+	switchtec_dma_process_desc(swdma_chan);
+
+	return dma_cookie_status(chan, cookie, txstate);
+}
+
+static void switchtec_dma_issue_pending(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
+
+	/*
+	 * Ensure the desc updates are visible before starting the
+	 * DMA engine.
+	 */
+	wmb();
+
+	/*
+	 * The sq_tail register is actually for the head of the
+	 * submisssion queue. Chip has the opposite define of head/tail
+	 * to the Linux kernel.
+	 */
+
+	rcu_read_lock();
+	if (!rcu_dereference(swdma_dev->pdev)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	spin_lock_bh(&swdma_chan->submit_lock);
+	writew(swdma_chan->head, &swdma_chan->mmio_chan_hw->sq_tail);
+	spin_unlock_bh(&swdma_chan->submit_lock);
+
+	rcu_read_unlock();
+}
+
+static irqreturn_t switchtec_dma_isr(int irq, void *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = chan;
+
+	if (swdma_chan->comp_ring_active)
+		tasklet_schedule(&swdma_chan->desc_task);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t switchtec_dma_chan_status_isr(int irq, void *dma)
+{
+	struct switchtec_dma_dev *swdma_dev = dma;
+
+	tasklet_schedule(&swdma_dev->chan_status_task);
+
+	return IRQ_HANDLED;
+}
+
+static void switchtec_dma_free_desc(struct switchtec_dma_chan *swdma_chan)
+{
+	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
+	size_t size;
+	int i;
+
+	size = SWITCHTEC_DMA_SQ_SIZE * sizeof(*swdma_chan->hw_sq);
+	if (swdma_chan->hw_sq)
+		dma_free_coherent(swdma_dev->dma_dev.dev, size,
+				  swdma_chan->hw_sq, swdma_chan->dma_addr_sq);
+
+	size = SWITCHTEC_DMA_CQ_SIZE * sizeof(*swdma_chan->hw_cq);
+	if (swdma_chan->hw_cq)
+		dma_free_coherent(swdma_dev->dma_dev.dev, size,
+				  swdma_chan->hw_cq, swdma_chan->dma_addr_cq);
+
+	if (swdma_chan->desc_ring) {
+		for (i = 0; i < SWITCHTEC_DMA_RING_SIZE; i++)
+			kfree(swdma_chan->desc_ring[i]);
+
+		kfree(swdma_chan->desc_ring);
+	}
+}
+
+static int switchtec_dma_alloc_desc(struct switchtec_dma_chan *swdma_chan)
+{
+	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
+	struct pci_dev *pdev;
+	struct chan_fw_regs __iomem *chan_fw = swdma_chan->mmio_chan_fw;
+	size_t size;
+	struct switchtec_dma_desc *desc;
+	int rc;
+	int i;
+
+	swdma_chan->head = swdma_chan->tail = 0;
+	swdma_chan->cq_tail = 0;
+
+	size = SWITCHTEC_DMA_SQ_SIZE * sizeof(*swdma_chan->hw_sq);
+	swdma_chan->hw_sq = dma_alloc_coherent(swdma_dev->dma_dev.dev, size,
+					       &swdma_chan->dma_addr_sq,
+					       GFP_KERNEL);
+	if (!swdma_chan->hw_sq) {
+		rc = -ENOMEM;
+		goto free_and_exit;
+	}
+
+	size = SWITCHTEC_DMA_CQ_SIZE * sizeof(*swdma_chan->hw_cq);
+	swdma_chan->hw_cq = dma_alloc_coherent(swdma_dev->dma_dev.dev, size,
+					       &swdma_chan->dma_addr_cq,
+					       GFP_KERNEL);
+	if (!swdma_chan->hw_cq) {
+		rc = -ENOMEM;
+		goto free_and_exit;
+	}
+
+	/* reset host phase tag */
+	swdma_chan->phase_tag = 0;
+
+	size = sizeof(*swdma_chan->desc_ring);
+	swdma_chan->desc_ring = kcalloc(SWITCHTEC_DMA_RING_SIZE, size,
+					GFP_KERNEL);
+	if (!swdma_chan->desc_ring) {
+		rc = -ENOMEM;
+		goto free_and_exit;
+	}
+
+	for (i = 0; i < SWITCHTEC_DMA_RING_SIZE; i++) {
+		desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+		if (!desc) {
+			rc = -ENOMEM;
+			goto free_and_exit;
+		}
+
+		dma_async_tx_descriptor_init(&desc->txd, &swdma_chan->dma_chan);
+		desc->txd.tx_submit = switchtec_dma_tx_submit;
+		desc->hw = &swdma_chan->hw_sq[i];
+		desc->completed = true;
+
+		swdma_chan->desc_ring[i] = desc;
+	}
+
+	rcu_read_lock();
+	pdev = rcu_dereference(swdma_dev->pdev);
+	if (!pdev) {
+		rcu_read_unlock();
+		rc = -ENODEV;
+		goto free_and_exit;
+	}
+
+	/* set sq/cq */
+	writel(lower_32_bits(swdma_chan->dma_addr_sq), &chan_fw->sq_base_lo);
+	writel(upper_32_bits(swdma_chan->dma_addr_sq), &chan_fw->sq_base_hi);
+	writel(lower_32_bits(swdma_chan->dma_addr_cq), &chan_fw->cq_base_lo);
+	writel(upper_32_bits(swdma_chan->dma_addr_cq), &chan_fw->cq_base_hi);
+
+	writew(SWITCHTEC_DMA_SQ_SIZE, &swdma_chan->mmio_chan_fw->sq_size);
+	writew(SWITCHTEC_DMA_CQ_SIZE, &swdma_chan->mmio_chan_fw->cq_size);
+
+	rcu_read_unlock();
+	return 0;
+
+free_and_exit:
+	switchtec_dma_free_desc(swdma_chan);
+	return rc;
+}
+
+static int switchtec_dma_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+	struct switchtec_dma_dev *swdma_dev = swdma_chan->swdma_dev;
+	u32 perf_cfg;
+	int rc;
+
+	rc = switchtec_dma_alloc_desc(swdma_chan);
+	if (rc)
+		return rc;
+
+	rc = enable_channel(swdma_chan);
+	if (rc)
+		return rc;
+
+	rc = reset_channel(swdma_chan);
+	if (rc)
+		return rc;
+
+	rc = unhalt_channel(swdma_chan);
+	if (rc)
+		return rc;
+
+	swdma_chan->ring_active = true;
+	swdma_chan->comp_ring_active = true;
+	swdma_chan->cid = 0;
+
+	dma_cookie_init(chan);
+
+	rcu_read_lock();
+	if (!rcu_dereference(swdma_dev->pdev)) {
+		rcu_read_unlock();
+		return -ENODEV;
+	}
+
+	perf_cfg = readl(&swdma_chan->mmio_chan_fw->perf_cfg);
+	rcu_read_unlock();
+
+	dev_dbg(&chan->dev->device, "Burst Size:  0x%x",
+		(perf_cfg >> PERF_BURST_SIZE_SHIFT) & PERF_BURST_SIZE_MASK);
+
+	dev_dbg(&chan->dev->device, "Burst Scale: 0x%x",
+		(perf_cfg >> PERF_BURST_SCALE_SHIFT) & PERF_BURST_SCALE_MASK);
+
+	dev_dbg(&chan->dev->device, "Interval:    0x%x",
+		(perf_cfg >> PERF_INTERVAL_SHIFT) & PERF_INTERVAL_MASK);
+
+	dev_dbg(&chan->dev->device, "Arb Weight:  0x%x",
+		(perf_cfg >> PERF_ARB_WEIGHT_SHIFT) & PERF_ARB_WEIGHT_MASK);
+
+	dev_dbg(&chan->dev->device, "MRRS:        0x%x",
+		(perf_cfg >> PERF_MRRS_SHIFT) & PERF_MRRS_MASK);
+
+	return SWITCHTEC_DMA_SQ_SIZE;
+}
+
+static void switchtec_dma_free_chan_resources(struct dma_chan *chan)
+{
+	struct switchtec_dma_chan *swdma_chan = to_switchtec_dma_chan(chan);
+
+	spin_lock_bh(&swdma_chan->submit_lock);
+	swdma_chan->ring_active = false;
+	spin_unlock_bh(&swdma_chan->submit_lock);
+
+	spin_lock_bh(&swdma_chan->complete_lock);
+	swdma_chan->comp_ring_active = false;
+	spin_unlock_bh(&swdma_chan->complete_lock);
+
+	switchtec_dma_chan_stop(swdma_chan);
+
+	tasklet_kill(&swdma_chan->desc_task);
+
+	switchtec_dma_abort_desc(swdma_chan, 0);
+
+	switchtec_dma_free_desc(swdma_chan);
+
+	disable_channel(swdma_chan);
+}
+
+static int switchtec_dma_chan_init(struct switchtec_dma_dev *swdma_dev, int i)
+{
+	struct dma_device *dma = &swdma_dev->dma_dev;
+	struct pci_dev *pdev = rcu_dereference(swdma_dev->pdev);
+	struct dma_chan *chan;
+	struct switchtec_dma_chan *swdma_chan;
+	u32 perf_cfg;
+	u32 valid_en_se;
+	u32 thresh;
+	int se_buf_len;
+	int irq;
+	int rc;
+
+	swdma_chan = kzalloc(sizeof(*swdma_chan), GFP_KERNEL);
+	if (!swdma_chan)
+		return -ENOMEM;
+
+	swdma_chan->phase_tag = 0;
+	swdma_chan->index = i;
+	swdma_chan->swdma_dev = swdma_dev;
+
+	swdma_chan->mmio_chan_fw =
+		swdma_dev->bar + SWITCHTEC_DMAC_CHAN_CFG_STS_OFFSET +
+		i * SWITCHTEC_DMA_CHAN_FW_REGS_SIZE;
+	swdma_chan->mmio_chan_hw =
+		swdma_dev->bar + SWITCHTEC_DMAC_CHAN_CTRL_OFFSET +
+		i * SWITCHTEC_DMA_CHAN_HW_REGS_SIZE;
+
+	swdma_dev->swdma_chans[i] = swdma_chan;
+
+	rc = pause_reset_channel(swdma_chan);
+	if (rc)
+		goto free_and_exit;
+
+	perf_cfg = readl(&swdma_chan->mmio_chan_fw->perf_cfg);
+
+	/* init perf tuner */
+	perf_cfg = PERF_BURST_SCALE << PERF_BURST_SCALE_SHIFT;
+	perf_cfg |= PERF_MRRS << PERF_MRRS_SHIFT;
+	perf_cfg |= PERF_INTERVAL << PERF_INTERVAL_SHIFT;
+	perf_cfg |= PERF_BURST_SIZE << PERF_BURST_SIZE_SHIFT;
+	perf_cfg |= PERF_ARB_WEIGHT << PERF_ARB_WEIGHT_SHIFT;
+
+	writel(perf_cfg, &swdma_chan->mmio_chan_fw->perf_cfg);
+
+	valid_en_se = readl(&swdma_chan->mmio_chan_fw->valid_en_se);
+
+	dev_dbg(&pdev->dev, "Channel %d: SE buffer base %d\n",
+		i, (valid_en_se >> SE_BUF_BASE_SHIFT) & SE_BUF_BASE_MASK);
+
+	se_buf_len = (valid_en_se >> SE_BUF_LEN_SHIFT) & SE_BUF_LEN_MASK;
+	dev_dbg(&pdev->dev, "Channel %d: SE buffer count %d\n", i, se_buf_len);
+
+	thresh = se_buf_len / 2;
+	valid_en_se |= (thresh & SE_THRESH_MASK) << SE_THRESH_SHIFT;
+	writel(valid_en_se, &swdma_chan->mmio_chan_fw->valid_en_se);
+
+	/* request irqs */
+	irq = readl(&swdma_chan->mmio_chan_fw->int_vec);
+	dev_dbg(&pdev->dev, "Channel %d: CE irq vector %d\n", i, irq);
+
+	rc = pci_request_irq(pdev, irq, switchtec_dma_isr, NULL, swdma_chan,
+			     KBUILD_MODNAME);
+	if (rc)
+		goto free_and_exit;
+
+	swdma_chan->irq = irq;
+
+	spin_lock_init(&swdma_chan->hw_ctrl_lock);
+	spin_lock_init(&swdma_chan->submit_lock);
+	spin_lock_init(&swdma_chan->complete_lock);
+	tasklet_init(&swdma_chan->desc_task, switchtec_dma_desc_task,
+		     (unsigned long)swdma_chan);
+
+	chan = &swdma_chan->dma_chan;
+	chan->device = dma;
+	dma_cookie_init(chan);
+
+	list_add_tail(&chan->device_node, &dma->channels);
+
+	return 0;
+
+free_and_exit:
+	kfree(swdma_chan);
+	return rc;
+}
+
+static int switchtec_dma_chan_free(struct switchtec_dma_chan *swdma_chan)
+{
+	struct pci_dev *pdev = rcu_dereference(swdma_chan->swdma_dev->pdev);
+
+	spin_lock_bh(&swdma_chan->submit_lock);
+	swdma_chan->ring_active = false;
+	spin_unlock_bh(&swdma_chan->submit_lock);
+
+	spin_lock_bh(&swdma_chan->complete_lock);
+	swdma_chan->comp_ring_active = false;
+	spin_unlock_bh(&swdma_chan->complete_lock);
+
+	pci_free_irq(pdev, swdma_chan->irq, swdma_chan);
+
+	switchtec_dma_chan_stop(swdma_chan);
+
+	return 0;
+}
+
+static int switchtec_dma_chans_release(struct switchtec_dma_dev *swdma_dev)
+{
+	int i;
+
+	for (i = 0; i < swdma_dev->chan_cnt; i++)
+		switchtec_dma_chan_free(swdma_dev->swdma_chans[i]);
+
+	return 0;
+}
+
+static int switchtec_dma_chans_enumerate(struct switchtec_dma_dev *swdma_dev,
+					 int chan_cnt)
+{
+	struct dma_device *dma = &swdma_dev->dma_dev;
+	struct pci_dev *pdev = rcu_dereference(swdma_dev->pdev);
+	int base;
+	int cnt;
+	int rc;
+	int i;
+
+	swdma_dev->swdma_chans = kcalloc(chan_cnt,
+					 sizeof(*swdma_dev->swdma_chans),
+					 GFP_KERNEL);
+
+	if (!swdma_dev->swdma_chans)
+		return -ENOMEM;
+
+	base = readw(swdma_dev->bar + SWITCHTEC_REG_SE_BUF_BASE);
+	cnt = readw(swdma_dev->bar + SWITCHTEC_REG_SE_BUF_CNT);
+
+	dev_dbg(&pdev->dev, "EP SE buffer base %d\n", base);
+	dev_dbg(&pdev->dev, "EP SE buffer count %d\n", cnt);
+
+	INIT_LIST_HEAD(&dma->channels);
+
+	for (i = 0; i < chan_cnt; i++) {
+		rc = switchtec_dma_chan_init(swdma_dev, i);
+		if (rc) {
+			dev_err(&pdev->dev, "Channel %d: init channel failed\n",
+				i);
+			chan_cnt = i;
+			goto err_exit;
+		}
+	}
+
+	return chan_cnt;
+
+err_exit:
+	for (i = 0; i < chan_cnt; i++)
+		switchtec_dma_chan_free(swdma_dev->swdma_chans[i]);
+
+	kfree(swdma_dev->swdma_chans);
+
+	return rc;
+}
+
+static void switchtec_dma_release(struct dma_device *dma_dev)
+{
+	int i;
+	struct switchtec_dma_dev *swdma_dev =
+		container_of(dma_dev, struct switchtec_dma_dev, dma_dev);
+
+	for (i = 0; i < swdma_dev->chan_cnt; i++)
+		kfree(swdma_dev->swdma_chans[i]);
+
+	kfree(swdma_dev->swdma_chans);
+
+	put_device(dma_dev->dev);
+	kfree(swdma_dev);
+}
+
+static int switchtec_dma_create(struct pci_dev *pdev)
+{
+	struct switchtec_dma_dev *swdma_dev;
+	struct dma_device *dma;
+	struct dma_chan *chan;
+	int chan_cnt;
+	int nr_vecs;
+	int irq;
+	int rc;
+
+	/*
+	 * Create the switchtec dma device
+	 */
+	swdma_dev = kzalloc(sizeof(*swdma_dev), GFP_KERNEL);
+	if (!swdma_dev)
+		return -ENOMEM;
+
+	swdma_dev->bar = ioremap(pci_resource_start(pdev, 0),
+				 pci_resource_len(pdev, 0));
+
+	pci_info(pdev, "Switchtec PSX/PFX DMA EP\n");
+
+	RCU_INIT_POINTER(swdma_dev->pdev, pdev);
+
+	nr_vecs = pci_msix_vec_count(pdev);
+	rc = pci_alloc_irq_vectors(pdev, nr_vecs, nr_vecs, PCI_IRQ_MSIX);
+	if (rc < 0)
+		goto err_exit;
+
+	tasklet_init(&swdma_dev->chan_status_task,
+		     switchtec_dma_chan_status_task,
+		     (unsigned long)swdma_dev);
+
+	irq = readw(swdma_dev->bar + SWITCHTEC_REG_CHAN_STS_VEC);
+	pci_dbg(pdev, "Channel pause irq vector %d\n", irq);
+
+	rc = pci_request_irq(pdev, irq, switchtec_dma_chan_status_isr, NULL,
+			     swdma_dev, KBUILD_MODNAME);
+	if (rc)
+		goto err_exit;
+
+	swdma_dev->chan_status_irq = irq;
+
+	chan_cnt = readl(swdma_dev->bar + SWITCHTEC_REG_CHAN_CNT);
+	if (!chan_cnt) {
+		pci_err(pdev, "No channel configured.\n");
+		rc = -ENXIO;
+		goto err_exit;
+	}
+
+	chan_cnt = switchtec_dma_chans_enumerate(swdma_dev, chan_cnt);
+	if (chan_cnt < 0) {
+		pci_err(pdev, "Failed to enumerate dma channels: %d\n",
+			chan_cnt);
+		rc = -ENXIO;
+		goto err_exit;
+	}
+
+	swdma_dev->chan_cnt = chan_cnt;
+
+	dma = &swdma_dev->dma_dev;
+	dma->copy_align = DMAENGINE_ALIGN_1_BYTE;
+	dma_cap_set(DMA_MEMCPY, dma->cap_mask);
+	dma_cap_set(DMA_PRIVATE, dma->cap_mask);
+	dma->dev = get_device(&pdev->dev);
+
+	dma->device_alloc_chan_resources = switchtec_dma_alloc_chan_resources;
+	dma->device_free_chan_resources = switchtec_dma_free_chan_resources;
+	dma->device_prep_dma_memcpy = switchtec_dma_prep_memcpy;
+	dma->device_prep_dma_imm_data = switchtec_dma_prep_wimm_data;
+	dma->device_issue_pending = switchtec_dma_issue_pending;
+	dma->device_tx_status = switchtec_dma_tx_status;
+	dma->device_pause = switchtec_dma_pause;
+	dma->device_resume = switchtec_dma_resume;
+	dma->device_terminate_all = switchtec_dma_terminate_all;
+	dma->device_synchronize = switchtec_dma_synchronize;
+	dma->device_release = switchtec_dma_release;
+
+	rc = dma_async_device_register(dma);
+	if (rc) {
+		pci_err(pdev, "Failed to register dma device: %d\n", rc);
+		goto err_chans_release_exit;
+	}
+
+	pci_info(pdev, "Channel count: %d\n", chan_cnt);
+
+	list_for_each_entry(chan, &dma->channels, device_node)
+		pci_info(pdev, "%s\n", dma_chan_name(chan));
+
+	pci_set_drvdata(pdev, swdma_dev);
+
+	return 0;
+
+err_chans_release_exit:
+	switchtec_dma_chans_release(swdma_dev);
+
+err_exit:
+	if (swdma_dev->chan_status_irq)
+		free_irq(swdma_dev->chan_status_irq, swdma_dev);
+
+	iounmap(swdma_dev->bar);
+	kfree(swdma_dev);
+	return rc;
+}
+
+static int switchtec_dma_probe(struct pci_dev *pdev,
+			       const struct pci_device_id *id)
+{
+	int rc;
+
+	rc = pci_enable_device(pdev);
+	if (rc)
+		return rc;
+
+	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+	if (rc)
+		goto err_disable;
+
+	rc = pci_request_mem_regions(pdev, KBUILD_MODNAME);
+	if (rc)
+		goto err_disable;
+
+	pci_set_master(pdev);
+
+	rc = switchtec_dma_create(pdev);
+	if (rc)
+		goto err_free;
+
+	pci_info(pdev, "Switchtec DMA Channels Registered\n");
+
+	return 0;
+
+err_free:
+	pci_free_irq_vectors(pdev);
+	pci_release_mem_regions(pdev);
+
+err_disable:
+	pci_disable_device(pdev);
+
+	return rc;
+}
+
+static void switchtec_dma_remove(struct pci_dev *pdev)
+{
+	struct switchtec_dma_dev *swdma_dev = pci_get_drvdata(pdev);
+
+	switchtec_dma_chans_release(swdma_dev);
+
+	tasklet_kill(&swdma_dev->chan_status_task);
+
+	rcu_assign_pointer(swdma_dev->pdev, NULL);
+	synchronize_rcu();
+
+	pci_free_irq(pdev, swdma_dev->chan_status_irq, swdma_dev);
+
+	pci_free_irq_vectors(pdev);
+
+	dma_async_device_unregister(&swdma_dev->dma_dev);
+
+	iounmap(swdma_dev->bar);
+	pci_release_mem_regions(pdev);
+	pci_disable_device(pdev);
+
+	pci_info(pdev, "Switchtec DMA Channels Unregistered\n");
+}
+
+/*
+ * Use vender/device and class to identify the DMA function.
+ */
+#define SWITCHTEC_DMA_DEVICE(device_id) \
+	{ \
+		.vendor     = PCI_VENDOR_ID_MICROSEMI, \
+		.device     = device_id, \
+		.subvendor  = PCI_ANY_ID, \
+		.subdevice  = PCI_ANY_ID, \
+		.class      = PCI_CLASS_SYSTEM_OTHER << 8, \
+		.class_mask = 0xFFFFFFFF, \
+	}
+
+static const struct pci_device_id switchtec_dma_pci_tbl[] = {
+	SWITCHTEC_DMA_DEVICE(0x4000), /* PFX 100XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4084), /* PFX 84XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4068), /* PFX 68XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4052), /* PFX 52XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4036), /* PFX 36XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4028), /* PFX 28XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4100), /* PSX 100XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4184), /* PSX 84XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4168), /* PSX 68XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4152), /* PSX 52XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4136), /* PSX 36XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4128), /* PSX 28XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4352), /* PFXA 52XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4336), /* PFXA 36XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4328), /* PFXA 28XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4452), /* PSXA 52XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4436), /* PSXA 36XG4 */
+	SWITCHTEC_DMA_DEVICE(0x4428), /* PSXA 28XG4 */
+	{0}
+};
+MODULE_DEVICE_TABLE(pci, switchtec_dma_pci_tbl);
+
+static struct pci_driver switchtec_dma_pci_driver = {
+	.name           = KBUILD_MODNAME,
+	.id_table       = switchtec_dma_pci_tbl,
+	.probe          = switchtec_dma_probe,
+	.remove		= switchtec_dma_remove,
+};
+module_pci_driver(switchtec_dma_pci_driver);