[PATCH 1/3] i2c: add DMA support for freescale i2c driver

[Yuan Yao <yao.yuan-KZfg59tc24xl57MIdRCFDg@public.gmane.org>]

Add dma support for i2c. This function depend on DMA driver.
You can turn on it by write both the dmas and dma-name properties in dts node.
And you should set ".has_dma_support" as true for dma support in imx_i2c_hwdata struct.

Signed-off-by: Yuan Yao <yao.yuan-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
---
 drivers/i2c/busses/i2c-imx.c | 358 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 344 insertions(+), 14 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index db895fb..6ec392b 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -37,22 +37,27 @@
 /** Includes *******************************************************************
 *******************************************************************************/
 
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/dmapool.h>
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
-#include <linux/delay.h>
 #include <linux/i2c.h>
+#include <linux/init.h>
 #include <linux/io.h>
-#include <linux/sched.h>
-#include <linux/platform_device.h>
-#include <linux/clk.h>
-#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/of_dma.h>
 #include <linux/platform_data/i2c-imx.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
 
 /** Defines ********************************************************************
 *******************************************************************************/
@@ -63,6 +68,9 @@
 /* Default value */
 #define IMX_I2C_BIT_RATE	100000	/* 100kHz */
 
+/* enable DMA if transfer size is bigger than this threshold */
+#define IMX_I2C_DMA_THRESHOLD	16
+
 /* IMX I2C registers:
  * the I2C register offset is different between SoCs,
  * to provid support for all these chips, split the
@@ -88,6 +96,7 @@
 #define I2SR_IBB	0x20
 #define I2SR_IAAS	0x40
 #define I2SR_ICF	0x80
+#define I2CR_DMAEN	0x02
 #define I2CR_RSTA	0x04
 #define I2CR_TXAK	0x08
 #define I2CR_MTX	0x10
@@ -172,6 +181,17 @@ struct imx_i2c_hwdata {
 	unsigned		ndivs;
 	unsigned		i2sr_clr_opcode;
 	unsigned		i2cr_ien_opcode;
+	bool			has_dma_support;
+};
+
+struct imx_i2c_dma {
+	struct dma_chan		*chan_tx;
+	struct dma_chan		*chan_rx;
+	dma_addr_t		buf_tx;
+	dma_addr_t		buf_rx;
+	unsigned int		len_tx;
+	unsigned int		len_rx;
+	struct completion	cmd_complete;
 };
 
 struct imx_i2c_struct {
@@ -184,6 +204,9 @@ struct imx_i2c_struct {
 	int			stopped;
 	unsigned int		ifdr; /* IMX_I2C_IFDR */
 	const struct imx_i2c_hwdata	*hwdata;
+
+	bool			use_dma;
+	struct imx_i2c_dma	*dma;
 };
 
 static const struct imx_i2c_hwdata imx1_i2c_hwdata  = {
@@ -193,6 +216,7 @@ static const struct imx_i2c_hwdata imx1_i2c_hwdata  = {
 	.ndivs			= ARRAY_SIZE(imx_i2c_clk_div),
 	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W0C,
 	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_1,
+	.has_dma_support	= false,
 
 };
 
@@ -203,6 +227,7 @@ static const struct imx_i2c_hwdata imx21_i2c_hwdata  = {
 	.ndivs			= ARRAY_SIZE(imx_i2c_clk_div),
 	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W0C,
 	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_1,
+	.has_dma_support	= false,
 
 };
 
@@ -213,6 +238,7 @@ static struct imx_i2c_hwdata vf610_i2c_hwdata = {
 	.ndivs			= ARRAY_SIZE(vf610_i2c_clk_div),
 	.i2sr_clr_opcode	= I2SR_CLR_OPCODE_W1C,
 	.i2cr_ien_opcode	= I2CR_IEN_OPCODE_0,
+	.has_dma_support	= true,
 
 };
 
@@ -254,6 +280,155 @@ static inline unsigned char imx_i2c_read_reg(struct imx_i2c_struct *i2c_imx,
 	return readb(i2c_imx->base + (reg << i2c_imx->hwdata->regshift));
 }
 
+/** Functions for DMA support ************************************************
+******************************************************************************/
+static int i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx, u32 phy_addr)
+{
+	struct imx_i2c_dma *dma = i2c_imx->dma;
+	struct dma_slave_config dma_sconfig;
+	int ret;
+
+	dma->chan_tx = dma_request_slave_channel(&i2c_imx->adapter.dev, "tx");
+	if (!dma->chan_tx) {
+		dev_err(&i2c_imx->adapter.dev,
+				"Dma tx channel request failed!\n");
+		return -ENODEV;
+	}
+
+	dma_sconfig.dst_addr = (dma_addr_t)phy_addr +
+				(IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
+	dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	dma_sconfig.dst_maxburst = 1;
+	dma_sconfig.direction = DMA_MEM_TO_DEV;
+	ret = dmaengine_slave_config(dma->chan_tx, &dma_sconfig);
+	if (ret < 0) {
+		dev_err(&i2c_imx->adapter.dev,
+				"Dma slave config failed, err = %d\n", ret);
+		dma_release_channel(dma->chan_tx);
+		return ret;
+	}
+
+	dma->chan_rx = dma_request_slave_channel(&i2c_imx->adapter.dev, "rx");
+	if (!dma->chan_rx) {
+		dev_err(&i2c_imx->adapter.dev,
+				"Dma rx channel request failed!\n");
+		return -ENODEV;
+	}
+
+	dma_sconfig.src_addr = (dma_addr_t)phy_addr +
+				(IMX_I2C_I2DR << i2c_imx->hwdata->regshift);
+	dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	dma_sconfig.src_maxburst = 1;
+	dma_sconfig.direction = DMA_DEV_TO_MEM;
+	ret = dmaengine_slave_config(dma->chan_rx, &dma_sconfig);
+	if (ret < 0) {
+		dev_err(&i2c_imx->adapter.dev,
+				"Dma slave config failed, err = %d\n", ret);
+		dma_release_channel(dma->chan_rx);
+		return ret;
+	}
+
+	init_completion(&dma->cmd_complete);
+
+	return 0;
+}
+
+static void i2c_imx_dma_tx_callback(void *arg)
+{
+	struct imx_i2c_struct *i2c_imx = (struct imx_i2c_struct *)arg;
+	struct imx_i2c_dma *dma = i2c_imx->dma;
+
+	dma_unmap_single(dma->chan_tx->device->dev, dma->buf_tx,
+			dma->len_tx, DMA_TO_DEVICE);
+	complete(&dma->cmd_complete);
+}
+
+static int i2c_imx_dma_tx(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
+{
+	struct imx_i2c_dma *dma = i2c_imx->dma;
+	struct dma_async_tx_descriptor *txdesc;
+
+	dma->len_tx = msgs->len-1;
+	dma->buf_tx = dma_map_single(dma->chan_tx->device->dev, msgs->buf,
+					dma->len_tx, DMA_TO_DEVICE);
+	if (dma_mapping_error(dma->chan_tx->device->dev, dma->buf_tx)) {
+		dev_err(&i2c_imx->adapter.dev, "dma_map_single tx failed\n");
+		return -EINVAL;
+	}
+
+	txdesc = dmaengine_prep_slave_single(dma->chan_tx, dma->buf_tx,
+					dma->len_tx, DMA_MEM_TO_DEV,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!txdesc) {
+		dev_err(&i2c_imx->adapter.dev,
+				"Not able to get desc for tx\n");
+		return -EINVAL;
+	}
+
+	txdesc->callback = i2c_imx_dma_tx_callback;
+	txdesc->callback_param = i2c_imx;
+	dmaengine_submit(txdesc);
+	dma_async_issue_pending(dma->chan_tx);
+	
+	return 0;
+}
+
+static void i2c_imx_dma_rx_callback(void *arg)
+{
+	struct imx_i2c_struct *i2c_imx = (struct imx_i2c_struct *)arg;
+	struct imx_i2c_dma *dma = i2c_imx->dma;
+
+	dma_unmap_single(dma->chan_rx->device->dev, dma->buf_rx,
+				dma->len_rx, DMA_FROM_DEVICE);
+	complete(&dma->cmd_complete);
+}
+
+static int i2c_imx_dma_rx(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
+{
+	struct imx_i2c_dma *dma = i2c_imx->dma;
+	struct dma_async_tx_descriptor *txdesc;
+
+	dma->len_rx = msgs->len - 2;
+	dma->buf_rx = dma_map_single(dma->chan_rx->device->dev, msgs->buf,
+					dma->len_rx, DMA_FROM_DEVICE);
+	if (dma_mapping_error(dma->chan_rx->device->dev, dma->buf_rx)) {
+		dev_err(&i2c_imx->adapter.dev, "dma_map_single tx failed\n");
+		return -EINVAL;
+	}
+
+	txdesc = dmaengine_prep_slave_single(dma->chan_rx, dma->buf_rx,
+					dma->len_rx, DMA_DEV_TO_MEM,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!txdesc) {
+		dev_err(&i2c_imx->adapter.dev,
+				"Not able to get desc for rx\n");
+		return -EINVAL;
+	}
+
+	txdesc->callback = i2c_imx_dma_rx_callback;
+	txdesc->callback_param = i2c_imx;
+	dmaengine_submit(txdesc);
+	dma_async_issue_pending(dma->chan_rx);
+	
+	return 0;
+}
+static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx)
+{
+	struct imx_i2c_dma *dma = i2c_imx->dma;
+	struct dma_chan *dma_chan;
+
+	dma_chan = dma->chan_tx;
+	dma->chan_tx = NULL;
+	dma->buf_tx = 0;
+	dma->len_tx = 0;
+	dma_release_channel(dma_chan);
+
+	dma_chan = dma->chan_rx;
+	dma->chan_tx = NULL;
+	dma->buf_rx = 0;
+	dma->len_rx = 0;
+	dma_release_channel(dma_chan);
+}
 /** Functions for IMX I2C adapter driver ***************************************
 *******************************************************************************/
 
@@ -425,7 +600,8 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
 	return IRQ_NONE;
 }
 
-static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
+static int i2c_imx_pio_write(struct imx_i2c_struct *i2c_imx,
+							struct i2c_msg *msgs)
 {
 	int i, result;
 
@@ -458,7 +634,56 @@ static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
 	return 0;
 }
 
-static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
+static int i2c_imx_dma_write(struct imx_i2c_struct *i2c_imx,
+							struct i2c_msg *msgs)
+{
+	int result, timeout=1000;
+	unsigned int temp = 0;
+
+	reinit_completion(&i2c_imx->dma->cmd_complete);
+	result = i2c_imx_dma_tx(i2c_imx, msgs);
+	if(result)
+		return result;
+
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp |= I2CR_DMAEN;
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+	/* write slave address */
+	imx_i2c_write_reg(msgs->addr << 1, i2c_imx, IMX_I2C_I2DR);
+	result = wait_for_completion_interruptible_timeout(
+						&i2c_imx->dma->cmd_complete,
+						msecs_to_jiffies(1000));
+	if (result == 0)
+		return  -ETIMEDOUT;
+
+	/* waiting for Transfer complete. */
+	while(timeout--) {
+		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
+		if (temp & 0x80)
+			break;
+		udelay(10);
+	}
+
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~I2CR_DMAEN;
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+	/* write the last byte */
+	imx_i2c_write_reg(msgs->buf[msgs->len-1], i2c_imx, IMX_I2C_I2DR);
+	result = i2c_imx_trx_complete(i2c_imx);
+	if (result)
+		return result;
+
+	result = i2c_imx_acked(i2c_imx);
+	if (result)
+		return result;
+
+	return 0;
+}
+
+static int i2c_imx_pio_read(struct imx_i2c_struct *i2c_imx,
+							struct i2c_msg *msgs)
 {
 	int i, result;
 	unsigned int temp;
@@ -518,6 +743,80 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
 	return 0;
 }
 
+static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
+							struct i2c_msg *msgs)
+{
+	int result, timeout=1000;
+	unsigned int temp;
+
+	/* write slave address */
+	imx_i2c_write_reg((msgs->addr << 1) | 0x01, i2c_imx, IMX_I2C_I2DR);
+	result = i2c_imx_trx_complete(i2c_imx);
+	if (result)
+		return result;
+
+	result = i2c_imx_acked(i2c_imx);
+	if (result)
+		return result;
+
+	/* setup bus to read data */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~I2CR_MTX;
+	if (msgs->len - 1)
+		temp &= ~I2CR_TXAK;
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+	imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
+
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp |= I2CR_DMAEN;
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+	reinit_completion(&i2c_imx->dma->cmd_complete);
+	result = i2c_imx_dma_rx(i2c_imx, msgs);
+	if(result)
+		return result;
+
+	result = wait_for_completion_interruptible_timeout(
+						&i2c_imx->dma->cmd_complete,
+						msecs_to_jiffies(1000));
+	if (result == 0)
+		return  -ETIMEDOUT;
+
+	/* waiting for Transfer complete. */
+	while(timeout--) {
+		temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
+		if (temp & 0x80)
+			break;
+		udelay(10);
+	}
+
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~I2CR_DMAEN;
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+	/* read n-1 byte data */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp |= I2CR_TXAK;
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+	msgs->buf[msgs->len-2] = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+	/* read n byte data */
+	result = i2c_imx_trx_complete(i2c_imx);
+	if (result)
+		return result;
+
+	/* It must generate STOP before read I2DR to prevent
+	   controller from generating another clock cycle */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~(I2CR_MSTA | I2CR_MTX);
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+	i2c_imx_bus_busy(i2c_imx, 0);
+	i2c_imx->stopped = 1;
+	msgs->buf[msgs->len-1] = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+
+	return 0;
+}
+
 static int i2c_imx_xfer(struct i2c_adapter *adapter,
 						struct i2c_msg *msgs, int num)
 {
@@ -563,10 +862,18 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
 			(temp & I2SR_SRW ? 1 : 0), (temp & I2SR_IIF ? 1 : 0),
 			(temp & I2SR_RXAK ? 1 : 0));
 #endif
-		if (msgs[i].flags & I2C_M_RD)
-			result = i2c_imx_read(i2c_imx, &msgs[i]);
-		else
-			result = i2c_imx_write(i2c_imx, &msgs[i]);
+		if(i2c_imx->use_dma && msgs[i].len >= IMX_I2C_DMA_THRESHOLD) {
+			if (msgs[i].flags & I2C_M_RD)
+				result = i2c_imx_dma_read(i2c_imx, &msgs[i]);
+			else
+				result = i2c_imx_dma_write(i2c_imx, &msgs[i]);
+		} else {
+			if (msgs[i].flags & I2C_M_RD)
+				result = i2c_imx_pio_read(i2c_imx, &msgs[i]);
+			else
+				result = i2c_imx_pio_write(i2c_imx, &msgs[i]);
+		}
+
 		if (result)
 			goto fail0;
 	}
@@ -601,6 +908,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	void __iomem *base;
 	int irq, ret;
 	u32 bitrate;
+	u32 phy_addr;
 
 	dev_dbg(&pdev->dev, "<%s>\n", __func__);
 
@@ -611,6 +919,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
 	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	phy_addr = res->start;
 	base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(base))
 		return PTR_ERR(base);
@@ -696,6 +1005,24 @@ static int i2c_imx_probe(struct platform_device *pdev)
 		i2c_imx->adapter.name);
 	dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
 
+	/* Init DMA config if support*/
+	if (i2c_imx->hwdata->has_dma_support) {
+		dev_info(&pdev->dev, "has_dma_support_begin.\n");
+		i2c_imx->dma = devm_kzalloc(&pdev->dev, sizeof(struct imx_i2c_dma),
+				GFP_KERNEL);
+		if (!i2c_imx->dma) {
+			dev_info(&pdev->dev, "can't allocate dma struct faild use dma.\n");
+			i2c_imx->use_dma = false;
+		}
+		else if (i2c_imx_dma_request(i2c_imx, phy_addr)) {
+			dev_info(&pdev->dev, "can't request dma chan, faild use dma.\n");
+			i2c_imx->use_dma = false;
+		}
+		else {
+			i2c_imx->use_dma = true;
+		}
+	}
+
 	return 0;   /* Return OK */
 }
 
@@ -707,6 +1034,9 @@ static int i2c_imx_remove(struct platform_device *pdev)
 	dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n");
 	i2c_del_adapter(&i2c_imx->adapter);
 
+	if (i2c_imx->use_dma)
+		i2c_imx_dma_free(i2c_imx);
+
 	/* setup chip registers to defaults */
 	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_IADR);
 	imx_i2c_write_reg(0, i2c_imx, IMX_I2C_IFDR);
-- 
1.8.4