diff mbox series

[RFC,02/12] soc: qcom: ipa: DMA helpers

Message ID 20181107003250.5832-3-elder@linaro.org (mailing list archive)
State Superseded, archived
Headers show
Series net: introduce Qualcomm IPA driver | expand

Commit Message

Alex Elder Nov. 7, 2018, 12:32 a.m. UTC 
This patch includes code implementing the IPA DMA module, which
defines a structure to represent a DMA allocation for the IPA device.
It's used throughout the IPA code.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_dma.c | 61 +++++++++++++++++++++++++++++++++++++++
 drivers/net/ipa/ipa_dma.h | 61 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 122 insertions(+)
 create mode 100644 drivers/net/ipa/ipa_dma.c
 create mode 100644 drivers/net/ipa/ipa_dma.h

Comments

Arnd Bergmann Nov. 7, 2018, 12:17 p.m. UTC | #1 
On Wed, Nov 7, 2018 at 1:33 AM Alex Elder <elder@linaro.org> wrote:
>
> This patch includes code implementing the IPA DMA module, which
> defines a structure to represent a DMA allocation for the IPA device.
> It's used throughout the IPA code.
>
> Signed-off-by: Alex Elder <elder@linaro.org>

I looked through all the users of this and couldn't fine one that actually
benefits from it. I'd say better drop this patch entirely and open-code
the contents in the callers. That will help readability since the dma
API is well understood by many people.

Generally speaking, try not to wrap Linux interfaces into driver specific
helper functions.

      Arnd
Alex Elder Nov. 13, 2018, 4:33 p.m. UTC | #2 
On 11/7/18 6:17 AM, Arnd Bergmann wrote:
> On Wed, Nov 7, 2018 at 1:33 AM Alex Elder <elder@linaro.org> wrote:
>>
>> This patch includes code implementing the IPA DMA module, which
>> defines a structure to represent a DMA allocation for the IPA device.
>> It's used throughout the IPA code.
>>
>> Signed-off-by: Alex Elder <elder@linaro.org>
> 
> I looked through all the users of this and couldn't fine one that actually
> benefits from it. I'd say better drop this patch entirely and open-code
> the contents in the callers. That will help readability since the dma
> API is well understood by many people.

Originally this was done to make it more obvious that all DMA allocations
were done with the same device pointer.  Previously there were several
separate devices, and it wasn't very obvious that only one was used (and
required).  Now that we're past that it's not difficult to do as you suggest.

I have now done that, and in the process identified a few more ways to
improve/simplify the code.  The net result is that more lines of code
were removed than were present in "ipa_dma.[ch]".  I see that as a
win (aside from your point below).

> Generally speaking, try not to wrap Linux interfaces into driver specific
> helper functions.

Agreed.  Thanks a lot for your review.

					-Alex

> 
>       Arnd
>
diff mbox series

Patch

diff --git a/drivers/net/ipa/ipa_dma.c b/drivers/net/ipa/ipa_dma.c
new file mode 100644
index 000000000000..dfde59e5072a
--- /dev/null
+++ b/drivers/net/ipa/ipa_dma.c
@@ -0,0 +1,61 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (c) 2018, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2018 Linaro Ltd.
+ */
+
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/string.h>
+
+#include "ipa_dma.h"
+
+static struct device *ipa_dma_dev;
+
+int ipa_dma_init(struct device *dev, u32 align)
+{
+	int ret;
+
+	/* Ensure DMA addresses will have the alignment we require */
+	if (dma_get_cache_alignment() % align)
+		return -ENOTSUPP;
+
+	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
+	if (!ret)
+		ipa_dma_dev = dev;
+
+	return ret;
+}
+
+void ipa_dma_exit(void)
+{
+	ipa_dma_dev = NULL;
+}
+
+int ipa_dma_alloc(struct ipa_dma_mem *mem, size_t size, gfp_t gfp)
+{
+	dma_addr_t phys;
+	void *virt;
+
+	virt = dma_zalloc_coherent(ipa_dma_dev, size, &phys, gfp);
+	if (!virt)
+		return -ENOMEM;
+
+	mem->virt = virt;
+	mem->phys = phys;
+	mem->size = size;
+
+	return 0;
+}
+
+void ipa_dma_free(struct ipa_dma_mem *mem)
+{
+	dma_free_coherent(ipa_dma_dev, mem->size, mem->virt, mem->phys);
+	memset(mem, 0, sizeof(*mem));
+}
+
+void *ipa_dma_phys_to_virt(struct ipa_dma_mem *mem, dma_addr_t phys)
+{
+	return mem->virt + (phys - mem->phys);
+}
diff --git a/drivers/net/ipa/ipa_dma.h b/drivers/net/ipa/ipa_dma.h
new file mode 100644
index 000000000000..e211dbd9d4ec
--- /dev/null
+++ b/drivers/net/ipa/ipa_dma.h
@@ -0,0 +1,61 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (c) 2018, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2018 Linaro Ltd.
+ */
+#ifndef _IPA_DMA_H_
+#define _IPA_DMA_H_
+
+#include <linux/types.h>
+#include <linux/device.h>
+
+/**
+ * struct ipa_dma_mem - IPA allocated DMA memory descriptor
+ * @virt: host virtual base address of allocated DMA memory
+ * @phys: bus physical base address of DMA memory
+ * @size: size (bytes) of DMA memory
+ */
+struct ipa_dma_mem {
+	void *virt;
+	dma_addr_t phys;
+	size_t size;
+};
+
+/**
+ * ipa_dma_init() - Initialize IPA DMA system.
+ * @dev:	IPA device structure
+ * @align:	Hardware required alignment for DMA memory
+ *
+ * Returns:	 0 if successful, or a negative error code.
+ */
+int ipa_dma_init(struct device *dev, u32 align);
+
+/**
+ * ipa_dma_exit() - shut down/clean up IPA DMA system
+ */
+void ipa_dma_exit(void);
+
+/**
+ * ipa_dma_alloc() - allocate a DMA buffer, describe it in mem struct
+ * @mem:	Memory structure to fill with allocation information.
+ * @size:	Size of DMA buffer to allocate.
+ * @gfp:	Allocation mode.
+ */
+int ipa_dma_alloc(struct ipa_dma_mem *mem, size_t size, gfp_t gfp);
+
+/**
+ * ipa_dma_free() - free a previously-allocated DMA buffer
+ * @mem:	Information about DMA allocation to free
+ */
+void ipa_dma_free(struct ipa_dma_mem *mem);
+
+/**
+ * ipa_dma_phys_to_virt() - return the virtual equivalent of a DMA address
+ * @phys:	DMA allocation information
+ * @phys:	Physical address to convert
+ *
+ * Return:	Virtual address corresponding to the given physical address
+ */
+void *ipa_dma_phys_to_virt(struct ipa_dma_mem *mem, dma_addr_t phys);
+
+#endif /* !_IPA_DMA_H_ */