[1/1] spi_s3c24xx: Add FIQ pseudo-DMA support
diff mbox

Message ID 20091118231251.676440026@fluff.org.uk
State Accepted
Headers show

Commit Message

Ben Dooks Nov. 18, 2009, 11:12 p.m. UTC
None

Patch
diff mbox

Index: b/drivers/spi/Makefile
===================================================================
--- a/drivers/spi/Makefile	2009-11-18 15:53:44.000000000 +0000
+++ b/drivers/spi/Makefile	2009-11-18 15:55:17.000000000 +0000
@@ -28,11 +28,17 @@  obj-$(CONFIG_SPI_MPC52xx_PSC)		+= mpc52x
 obj-$(CONFIG_SPI_MPC8xxx)		+= spi_mpc8xxx.o
 obj-$(CONFIG_SPI_PPC4xx)		+= spi_ppc4xx.o
 obj-$(CONFIG_SPI_S3C24XX_GPIO)		+= spi_s3c24xx_gpio.o
-obj-$(CONFIG_SPI_S3C24XX)		+= spi_s3c24xx.o
+obj-$(CONFIG_SPI_S3C24XX)		+= spi_s3c24xx_hw.o
 obj-$(CONFIG_SPI_TXX9)			+= spi_txx9.o
 obj-$(CONFIG_SPI_XILINX)		+= xilinx_spi.o
 obj-$(CONFIG_SPI_SH_SCI)		+= spi_sh_sci.o
 obj-$(CONFIG_SPI_STMP3XXX)		+= spi_stmp.o
+
+# special build for s3c24xx spi driver with fiq support
+spi_s3c24xx_hw-y			:= spi_s3c24xx.o
+spi_s3c24xx_hw-$(CONFIG_SPI_S3C24XX_FIQ) += spi_s3c24xx_fiq.o
+
+
 # 	... add above this line ...
 
 # SPI protocol drivers (device/link on bus)
Index: b/drivers/spi/spi_s3c24xx_fiq.S
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ b/drivers/spi/spi_s3c24xx_fiq.S	2009-11-18 15:55:32.000000000 +0000
@@ -0,0 +1,116 @@ 
+/* linux/drivers/spi/spi_s3c24xx_fiq.S
+ *
+ * Copyright 2009 Simtec Electronics
+ *	Ben Dooks <ben@simtec.co.uk>
+ *
+ * S3C24XX SPI - FIQ pseudo-DMA transfer code
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+*/
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+#include <mach/map.h>
+#include <mach/regs-irq.h>
+#include <plat/regs-spi.h>
+
+#include "spi_s3c24xx_fiq.h"
+
+	.text
+
+	@ entry to these routines is as follows, with the register names
+	@ defined in fiq.h so that they can be shared with the C files which
+	@ setup the calling registers.
+	@
+	@ fiq_rirq	The base of the IRQ registers to find S3C2410_SRCPND
+	@ fiq_rtmp	Temporary register to hold tx/rx data
+	@ fiq_rspi	The base of the SPI register block
+	@ fiq_rtx	The tx buffer pointer
+	@ fiq_rrx	The rx buffer pointer
+	@ fiq_rcount	The number of bytes to move
+
+	@ each entry starts with a word entry of how long it is
+	@ and an offset to the irq acknowledgment word
+
+ENTRY(s3c24xx_spi_fiq_rx)
+s3c24xx_spi_fix_rx:
+	.word	fiq_rx_end - fiq_rx_start
+	.word	fiq_rx_irq_ack - fiq_rx_start
+fiq_rx_start:
+	ldr	fiq_rtmp, fiq_rx_irq_ack
+	str	fiq_rtmp, [ fiq_rirq, # S3C2410_SRCPND - S3C24XX_VA_IRQ ]
+
+	ldrb	fiq_rtmp, [ fiq_rspi, #  S3C2410_SPRDAT ]
+	strb	fiq_rtmp, [ fiq_rrx ], #1
+
+	mov	fiq_rtmp, #0xff
+	strb	fiq_rtmp, [ fiq_rspi, # S3C2410_SPTDAT ]
+
+	subs	fiq_rcount, fiq_rcount, #1
+	subnes	pc, lr, #4		@@ return, still have work to do
+
+	@@ set IRQ controller so that next op will trigger IRQ
+	mov	fiq_rtmp, #0
+	str	fiq_rtmp, [ fiq_rirq, # S3C2410_INTMOD  - S3C24XX_VA_IRQ ]
+	subs	pc, lr, #4
+
+fiq_rx_irq_ack:
+	.word	0
+fiq_rx_end:
+
+ENTRY(s3c24xx_spi_fiq_txrx)
+s3c24xx_spi_fiq_txrx:
+	.word	fiq_txrx_end - fiq_txrx_start
+	.word	fiq_txrx_irq_ack - fiq_txrx_start
+fiq_txrx_start:
+
+	ldrb	fiq_rtmp, [ fiq_rspi, #  S3C2410_SPRDAT ]
+	strb	fiq_rtmp, [ fiq_rrx ], #1
+
+	ldr	fiq_rtmp, fiq_txrx_irq_ack
+	str	fiq_rtmp, [ fiq_rirq, # S3C2410_SRCPND - S3C24XX_VA_IRQ ]
+
+	ldrb	fiq_rtmp, [ fiq_rtx ], #1
+	strb	fiq_rtmp, [ fiq_rspi, # S3C2410_SPTDAT ]
+
+	subs	fiq_rcount, fiq_rcount, #1
+	subnes	pc, lr, #4		@@ return, still have work to do
+
+	mov	fiq_rtmp, #0
+	str	fiq_rtmp, [ fiq_rirq, # S3C2410_INTMOD  - S3C24XX_VA_IRQ ]
+	subs	pc, lr, #4
+
+fiq_txrx_irq_ack:
+	.word	0
+
+fiq_txrx_end:
+
+ENTRY(s3c24xx_spi_fiq_tx)
+s3c24xx_spi_fix_tx:
+	.word	fiq_tx_end - fiq_tx_start
+	.word	fiq_tx_irq_ack - fiq_tx_start
+fiq_tx_start:
+	ldrb	fiq_rtmp, [ fiq_rspi, #  S3C2410_SPRDAT ]
+
+	ldr	fiq_rtmp, fiq_tx_irq_ack
+	str	fiq_rtmp, [ fiq_rirq, # S3C2410_SRCPND - S3C24XX_VA_IRQ ]
+
+	ldrb	fiq_rtmp, [ fiq_rtx ], #1
+	strb	fiq_rtmp, [ fiq_rspi, # S3C2410_SPTDAT ]
+
+	subs	fiq_rcount, fiq_rcount, #1
+	subnes	pc, lr, #4		@@ return, still have work to do
+
+	mov	fiq_rtmp, #0
+	str	fiq_rtmp, [ fiq_rirq, # S3C2410_INTMOD  - S3C24XX_VA_IRQ ]
+	subs	pc, lr, #4
+
+fiq_tx_irq_ack:
+	.word	0
+
+fiq_tx_end:
+
+	.end
Index: b/drivers/spi/Kconfig
===================================================================
--- a/drivers/spi/Kconfig	2009-11-18 15:53:44.000000000 +0000
+++ b/drivers/spi/Kconfig	2009-11-18 15:55:17.000000000 +0000
@@ -205,6 +205,17 @@  config SPI_S3C24XX
 	help
 	  SPI driver for Samsung S3C24XX series ARM SoCs
 
+config SPI_S3C24XX_FIQ
+	bool "S3C24XX driver with FIQ pseudo-DMA"
+	depends on SPI_S3C24XX
+	select FIQ
+	help
+	  Enable FIQ support for the S3C24XX SPI driver to provide pseudo
+	  DMA by using the fast-interrupt request framework, This allows
+	  the driver to get DMA-like performance when there are either
+	  no free DMA channels, or when doing transfers that required both
+	  TX and RX data paths.
+
 config SPI_S3C24XX_GPIO
 	tristate "Samsung S3C24XX series SPI by GPIO"
 	depends on ARCH_S3C2410 && EXPERIMENTAL
Index: b/drivers/spi/spi_s3c24xx.c
===================================================================
--- a/drivers/spi/spi_s3c24xx.c	2009-11-18 15:53:44.000000000 +0000
+++ b/drivers/spi/spi_s3c24xx.c	2009-11-18 15:55:23.000000000 +0000
@@ -1,7 +1,7 @@ 
 /* linux/drivers/spi/spi_s3c24xx.c
  *
  * Copyright (c) 2006 Ben Dooks
- * Copyright (c) 2006 Simtec Electronics
+ * Copyright 2006-2009 Simtec Electronics
  *	Ben Dooks <ben@simtec.co.uk>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -28,6 +28,11 @@ 
 #include <plat/regs-spi.h>
 #include <mach/spi.h>
 
+#include <plat/fiq.h>
+#include <asm/fiq.h>
+
+#include "spi_s3c24xx_fiq.h"
+
 /**
  * s3c24xx_spi_devstate - per device data
  * @hz: Last frequency calculated for @sppre field.
@@ -42,6 +47,13 @@  struct s3c24xx_spi_devstate {
 	u8		sppre;
 };
 
+enum spi_fiq_mode {
+	FIQ_MODE_NONE	= 0,
+	FIQ_MODE_TX	= 1,
+	FIQ_MODE_RX	= 2,
+	FIQ_MODE_TXRX	= 3,
+};
+
 struct s3c24xx_spi {
 	/* bitbang has to be first */
 	struct spi_bitbang	 bitbang;
@@ -52,6 +64,11 @@  struct s3c24xx_spi {
 	int			 len;
 	int			 count;
 
+	struct fiq_handler	 fiq_handler;
+	enum spi_fiq_mode	 fiq_mode;
+	unsigned char		 fiq_inuse;
+	unsigned char		 fiq_claimed;
+
 	void			(*set_cs)(struct s3c2410_spi_info *spi,
 					  int cs, int pol);
 
@@ -67,6 +84,7 @@  struct s3c24xx_spi {
 	struct s3c2410_spi_info *pdata;
 };
 
+
 #define SPCON_DEFAULT (S3C2410_SPCON_MSTR | S3C2410_SPCON_SMOD_INT)
 #define SPPIN_DEFAULT (S3C2410_SPPIN_KEEP)
 
@@ -127,7 +145,7 @@  static int s3c24xx_spi_update_state(stru
 	}
 
 	if (spi->mode != cs->mode) {
-		u8 spcon = SPCON_DEFAULT;
+		u8 spcon = SPCON_DEFAULT | S3C2410_SPCON_ENSCK;
 
 		if (spi->mode & SPI_CPHA)
 			spcon |= S3C2410_SPCON_CPHA_FMTB;
@@ -214,13 +232,196 @@  static inline unsigned int hw_txbyte(str
 	return hw->tx ? hw->tx[count] : 0;
 }
 
+#ifdef CONFIG_SPI_S3C24XX_FIQ
+/* Support for FIQ based pseudo-DMA to improve the transfer speed.
+ *
+ * This code uses the assembly helper in spi_s3c24xx_spi.S which is
+ * used by the FIQ core to move data between main memory and the peripheral
+ * block. Since this is code running on the processor, there is no problem
+ * with cache coherency of the buffers, so we can use any buffer we like.
+ */
+
+/**
+ * struct spi_fiq_code - FIQ code and header
+ * @length: The length of the code fragment, excluding this header.
+ * @ack_offset: The offset from @data to the word to place the IRQ ACK bit at.
+ * @data: The code itself to install as a FIQ handler.
+ */
+struct spi_fiq_code {
+	u32	length;
+	u32	ack_offset;
+	u8	data[0];
+};
+
+extern struct spi_fiq_code s3c24xx_spi_fiq_txrx;
+extern struct spi_fiq_code s3c24xx_spi_fiq_tx;
+extern struct spi_fiq_code s3c24xx_spi_fiq_rx;
+
+/**
+ * ack_bit - turn IRQ into IRQ acknowledgement bit
+ * @irq: The interrupt number
+ *
+ * Returns the bit to write to the interrupt acknowledge register.
+ */
+static inline u32 ack_bit(unsigned int irq)
+{
+	return 1 << (irq - IRQ_EINT0);
+}
+
+/**
+ * s3c24xx_spi_tryfiq - attempt to claim and setup FIQ for transfer
+ * @hw: The hardware state.
+ *
+ * Claim the FIQ handler (only one can be active at any one time) and
+ * then setup the correct transfer code for this transfer.
+ *
+ * This call updates all the necessary state information if sucessful,
+ * so the caller does not need to do anything more than start the transfer
+ * as normal, since the IRQ will have been re-routed to the FIQ handler.
+*/
+void s3c24xx_spi_tryfiq(struct s3c24xx_spi *hw)
+{
+	struct pt_regs regs;
+	enum spi_fiq_mode mode;
+	struct spi_fiq_code *code;
+	int ret;
+
+	if (!hw->fiq_claimed) {
+		/* try and claim fiq if we haven't got it, and if not
+		 * then return and simply use another transfer method */
+
+		ret = claim_fiq(&hw->fiq_handler);
+		if (ret)
+			return;
+	}
+
+	if (hw->tx && !hw->rx)
+		mode = FIQ_MODE_TX;
+	else if (hw->rx && !hw->tx)
+		mode = FIQ_MODE_RX;
+	else
+		mode = FIQ_MODE_TXRX;
+
+	regs.uregs[fiq_rspi] = (long)hw->regs;
+	regs.uregs[fiq_rrx]  = (long)hw->rx;
+	regs.uregs[fiq_rtx]  = (long)hw->tx + 1;
+	regs.uregs[fiq_rcount] = hw->len - 1;
+	regs.uregs[fiq_rirq] = (long)S3C24XX_VA_IRQ;
+
+	set_fiq_regs(&regs);
+
+	if (hw->fiq_mode != mode) {
+		u32 *ack_ptr;
+
+		hw->fiq_mode = mode;
+
+		switch (mode) {
+		case FIQ_MODE_TX:
+			code = &s3c24xx_spi_fiq_tx;
+			break;
+		case FIQ_MODE_RX:
+			code = &s3c24xx_spi_fiq_rx;
+			break;
+		case FIQ_MODE_TXRX:
+			code = &s3c24xx_spi_fiq_txrx;
+			break;
+		default:
+			code = NULL;
+		}
+
+		BUG_ON(!code);
+
+		ack_ptr = (u32 *)&code->data[code->ack_offset];
+		*ack_ptr = ack_bit(hw->irq);
+
+		set_fiq_handler(&code->data, code->length);
+	}
+
+	s3c24xx_set_fiq(hw->irq, true);
+
+	hw->fiq_mode = mode;
+	hw->fiq_inuse = 1;
+}
+
+/**
+ * s3c24xx_spi_fiqop - FIQ core code callback
+ * @pw: Data registered with the handler
+ * @release: Whether this is a release or a return.
+ *
+ * Called by the FIQ code when another module wants to use the FIQ, so
+ * return whether we are currently using this or not and then update our
+ * internal state.
+ */
+static int s3c24xx_spi_fiqop(void *pw, int release)
+{
+	struct s3c24xx_spi *hw = pw;
+	int ret = 0;
+
+	if (release) {
+		if (hw->fiq_inuse)
+			ret = -EBUSY;
+
+		/* note, we do not need to unroute the FIQ, as the FIQ
+		 * vector code de-routes it to signal the end of transfer */
+
+		hw->fiq_mode = FIQ_MODE_NONE;
+		hw->fiq_claimed = 0;
+	} else {
+		hw->fiq_claimed = 1;
+	}
+
+	return ret;
+}
+
+/**
+ * s3c24xx_spi_initfiq - setup the information for the FIQ core
+ * @hw: The hardware state.
+ *
+ * Setup the fiq_handler block to pass to the FIQ core.
+ */
+static inline void s3c24xx_spi_initfiq(struct s3c24xx_spi *hw)
+{
+	hw->fiq_handler.dev_id = hw;
+	hw->fiq_handler.name = dev_name(hw->dev);
+	hw->fiq_handler.fiq_op = s3c24xx_spi_fiqop;
+}
+
+/**
+ * s3c24xx_spi_usefiq - return if we should be using FIQ.
+ * @hw: The hardware state.
+ *
+ * Return true if the platform data specifies whether this channel is
+ * allowed to use the FIQ.
+ */
+static inline bool s3c24xx_spi_usefiq(struct s3c24xx_spi *hw)
+{
+	return hw->pdata->use_fiq;
+}
+
+/**
+ * s3c24xx_spi_usingfiq - return if channel is using FIQ
+ * @spi: The hardware state.
+ *
+ * Return whether the channel is currently using the FIQ (separate from
+ * whether the FIQ is claimed).
+ */
+static inline bool s3c24xx_spi_usingfiq(struct s3c24xx_spi *spi)
+{
+	return spi->fiq_inuse;
+}
+#else
+
+static inline void s3c24xx_spi_initfiq(struct s3c24xx_spi *s) { }
+static inline void s3c24xx_spi_tryfiq(struct s3c24xx_spi *s) { }
+static inline bool s3c24xx_spi_usefiq(struct s3c24xx_spi *s) { return false; }
+static inline bool s3c24xx_spi_usingfiq(struct s3c24xx_spi *s) { return false; }
+
+#endif /* CONFIG_SPI_S3C24XX_FIQ */
+
 static int s3c24xx_spi_txrx(struct spi_device *spi, struct spi_transfer *t)
 {
 	struct s3c24xx_spi *hw = to_hw(spi);
 
-	dev_dbg(&spi->dev, "txrx: tx %p, rx %p, len %d\n",
-		t->tx_buf, t->rx_buf, t->len);
-
 	hw->tx = t->tx_buf;
 	hw->rx = t->rx_buf;
 	hw->len = t->len;
@@ -228,11 +429,14 @@  static int s3c24xx_spi_txrx(struct spi_d
 
 	init_completion(&hw->done);
 
+	hw->fiq_inuse = 0;
+	if (s3c24xx_spi_usefiq(hw) && t->len >= 3)
+		s3c24xx_spi_tryfiq(hw);
+
 	/* send the first byte */
 	writeb(hw_txbyte(hw, 0), hw->regs + S3C2410_SPTDAT);
 
 	wait_for_completion(&hw->done);
-
 	return hw->count;
 }
 
@@ -254,17 +458,27 @@  static irqreturn_t s3c24xx_spi_irq(int i
 		goto irq_done;
 	}
 
-	hw->count++;
+	if (!s3c24xx_spi_usingfiq(hw)) {
+		hw->count++;
 
-	if (hw->rx)
-		hw->rx[count] = readb(hw->regs + S3C2410_SPRDAT);
+		if (hw->rx)
+			hw->rx[count] = readb(hw->regs + S3C2410_SPRDAT);
 
-	count++;
+		count++;
+
+		if (count < hw->len)
+			writeb(hw_txbyte(hw, count), hw->regs + S3C2410_SPTDAT);
+		else
+			complete(&hw->done);
+	} else {
+		hw->count = hw->len;
+		hw->fiq_inuse = 0;
+
+		if (hw->rx)
+			hw->rx[hw->len-1] = readb(hw->regs + S3C2410_SPRDAT);
 
-	if (count < hw->len)
-		writeb(hw_txbyte(hw, count), hw->regs + S3C2410_SPTDAT);
-	else
 		complete(&hw->done);
+	}
 
  irq_done:
 	return IRQ_HANDLED;
@@ -322,6 +536,10 @@  static int __init s3c24xx_spi_probe(stru
 	platform_set_drvdata(pdev, hw);
 	init_completion(&hw->done);
 
+	/* initialise fiq handler */
+
+	s3c24xx_spi_initfiq(hw);
+
 	/* setup the master state. */
 
 	/* the spi->mode bits understood by this driver: */
Index: b/drivers/spi/spi_s3c24xx_fiq.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ b/drivers/spi/spi_s3c24xx_fiq.h	2009-11-18 15:55:38.000000000 +0000
@@ -0,0 +1,26 @@ 
+/* linux/drivers/spi/spi_s3c24xx_fiq.h
+ *
+ * Copyright 2009 Simtec Electronics
+ *	Ben Dooks <ben@simtec.co.uk>
+ *
+ * S3C24XX SPI - FIQ pseudo-DMA transfer support
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+*/
+
+/* We have R8 through R13 to play with */
+
+#ifdef __ASSEMBLY__
+#define __REG_NR(x)     r##x
+#else
+#define __REG_NR(x)     (x)
+#endif
+
+#define fiq_rspi	__REG_NR(8)
+#define fiq_rtmp	__REG_NR(9)
+#define fiq_rrx		__REG_NR(10)
+#define fiq_rtx		__REG_NR(11)
+#define fiq_rcount	__REG_NR(12)
+#define fiq_rirq	__REG_NR(13)
Index: b/arch/arm/mach-s3c2410/include/mach/spi.h
===================================================================
--- a/arch/arm/mach-s3c2410/include/mach/spi.h	2009-11-18 15:53:44.000000000 +0000
+++ b/arch/arm/mach-s3c2410/include/mach/spi.h	2009-11-18 15:55:17.000000000 +0000
@@ -18,6 +18,8 @@  struct s3c2410_spi_info {
 	unsigned int		 num_cs;	/* total chipselects */
 	int			 bus_num;       /* bus number to use. */
 
+	unsigned int		 use_fiq:1;	/* use fiq */
+
 	void (*gpio_setup)(struct s3c2410_spi_info *spi, int enable);
 	void (*set_cs)(struct s3c2410_spi_info *spi, int cs, int pol);
 };