[PATCH v3] spi: spi-fsl-dspi: Add DMA support for Vybrid

[Sanchayan Maity <maitysanchayan@gmail.com>]

Add DMA support for Vybrid.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
---
Changes since v2:
1. Rebase on top of Shawn's latest for-next branch
2. Make DMA mode the default for Vybrid. We no longer use the EOQ mode.
Since devtype_data has been constantified it's no longer makes sense to
change the trans_mode at run time.

Tested on Toradex Colibri Vybrid VF61 module using spidev and MCP CAN.

v1 Patch:
https://patchwork.kernel.org/patch/9360583/

v2 Patch:
https://patchwork.kernel.org/patch/9361601/

Regards,
Sanchayan.
---
 drivers/spi/spi-fsl-dspi.c | 301 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 300 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 35c0dd9..bc64700 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -15,6 +15,8 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/interrupt.h>
@@ -40,6 +42,7 @@
 #define TRAN_STATE_WORD_ODD_NUM	0x04
 
 #define DSPI_FIFO_SIZE			4
+#define DSPI_DMA_BUFSIZE		(DSPI_FIFO_SIZE * 1024)
 
 #define SPI_MCR		0x00
 #define SPI_MCR_MASTER		(1 << 31)
@@ -71,6 +74,11 @@
 #define SPI_SR_EOQF		0x10000000
 #define SPI_SR_TCFQF		0x80000000
 
+#define SPI_RSER_TFFFE		BIT(25)
+#define SPI_RSER_TFFFD		BIT(24)
+#define SPI_RSER_RFDFE		BIT(17)
+#define SPI_RSER_RFDFD		BIT(16)
+
 #define SPI_RSER		0x30
 #define SPI_RSER_EOQFE		0x10000000
 #define SPI_RSER_TCFQE		0x80000000
@@ -108,6 +116,8 @@
 
 #define SPI_TCR_TCNT_MAX	0x10000
 
+#define DMA_COMPLETION_TIMEOUT	msecs_to_jiffies(3000)
+
 struct chip_data {
 	u32 mcr_val;
 	u32 ctar_val;
@@ -117,6 +127,7 @@ struct chip_data {
 enum dspi_trans_mode {
 	DSPI_EOQ_MODE = 0,
 	DSPI_TCFQ_MODE,
+	DSPI_DMA_MODE,
 };
 
 struct fsl_dspi_devtype_data {
@@ -125,7 +136,7 @@ struct fsl_dspi_devtype_data {
 };
 
 static const struct fsl_dspi_devtype_data vf610_data = {
-	.trans_mode = DSPI_EOQ_MODE,
+	.trans_mode = DSPI_DMA_MODE,
 	.max_clock_factor = 2,
 };
 
@@ -139,6 +150,22 @@ static const struct fsl_dspi_devtype_data ls2085a_data = {
 	.max_clock_factor = 8,
 };
 
+struct fsl_dspi_dma {
+	u32 curr_xfer_len;
+
+	u32 *tx_dma_buf;
+	struct dma_chan *chan_tx;
+	dma_addr_t tx_dma_phys;
+	struct completion cmd_tx_complete;
+	struct dma_async_tx_descriptor *tx_desc;
+
+	u32 *rx_dma_buf;
+	struct dma_chan *chan_rx;
+	dma_addr_t rx_dma_phys;
+	struct completion cmd_rx_complete;
+	struct dma_async_tx_descriptor *rx_desc;
+};
+
 struct fsl_dspi {
 	struct spi_master	*master;
 	struct platform_device	*pdev;
@@ -165,6 +192,7 @@ struct fsl_dspi {
 	u32			waitflags;
 
 	u32			spi_tcnt;
+	struct fsl_dspi_dma	*dma;
 };
 
 static inline int is_double_byte_mode(struct fsl_dspi *dspi)
@@ -176,6 +204,263 @@ static inline int is_double_byte_mode(struct fsl_dspi *dspi)
 	return ((val & SPI_FRAME_BITS_MASK) == SPI_FRAME_BITS(8)) ? 0 : 1;
 }
 
+static void dspi_tx_dma_callback(void *arg)
+{
+	struct fsl_dspi *dspi = arg;
+	struct fsl_dspi_dma *dma = dspi->dma;
+
+	complete(&dma->cmd_tx_complete);
+}
+
+static void dspi_rx_dma_callback(void *arg)
+{
+	struct fsl_dspi *dspi = arg;
+	struct fsl_dspi_dma *dma = dspi->dma;
+	int rx_word;
+	int i, len;
+	u16 d;
+
+	rx_word = is_double_byte_mode(dspi);
+
+	len = rx_word ? (dma->curr_xfer_len / 2) : dma->curr_xfer_len;
+
+	if (!(dspi->dataflags & TRAN_STATE_RX_VOID)) {
+		for (i = 0; i < len; i++) {
+			d = dspi->dma->rx_dma_buf[i];
+			rx_word ? (*(u16 *)dspi->rx = d) :
+						(*(u8 *)dspi->rx = d);
+			dspi->rx += rx_word + 1;
+		}
+	}
+
+	complete(&dma->cmd_rx_complete);
+}
+
+static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
+{
+	struct fsl_dspi_dma *dma = dspi->dma;
+	struct device *dev = &dspi->pdev->dev;
+	int time_left;
+	int tx_word;
+	int i, len;
+	u16 val;
+
+	tx_word = is_double_byte_mode(dspi);
+
+	len = tx_word ? (dma->curr_xfer_len / 2) : dma->curr_xfer_len;
+
+	for (i = 0; i < len - 1; i++) {
+		val = tx_word ? *(u16 *) dspi->tx : *(u8 *) dspi->tx;
+		dspi->dma->tx_dma_buf[i] =
+			SPI_PUSHR_TXDATA(val) | SPI_PUSHR_PCS(dspi->cs) |
+			SPI_PUSHR_CTAS(0) | SPI_PUSHR_CONT;
+		dspi->tx += tx_word + 1;
+	}
+
+	val = tx_word ? *(u16 *) dspi->tx : *(u8 *) dspi->tx;
+	dspi->dma->tx_dma_buf[i] = SPI_PUSHR_TXDATA(val) |
+					SPI_PUSHR_PCS(dspi->cs) |
+					SPI_PUSHR_CTAS(0);
+	dspi->tx += tx_word + 1;
+
+	dma->tx_desc = dmaengine_prep_slave_single(dma->chan_tx,
+					dma->tx_dma_phys,
+					DSPI_DMA_BUFSIZE, DMA_MEM_TO_DEV,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!dma->tx_desc) {
+		dev_err(dev, "Not able to get desc for DMA xfer\n");
+		return -EIO;
+	}
+
+	dma->tx_desc->callback = dspi_tx_dma_callback;
+	dma->tx_desc->callback_param = dspi;
+	if (dma_submit_error(dmaengine_submit(dma->tx_desc))) {
+		dev_err(dev, "DMA submit failed\n");
+		return -EINVAL;
+	}
+
+	dma->rx_desc = dmaengine_prep_slave_single(dma->chan_rx,
+					dma->rx_dma_phys,
+					DSPI_DMA_BUFSIZE, DMA_DEV_TO_MEM,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!dma->rx_desc) {
+		dev_err(dev, "Not able to get desc for DMA xfer\n");
+		return -EIO;
+	}
+
+	dma->rx_desc->callback = dspi_rx_dma_callback;
+	dma->rx_desc->callback_param = dspi;
+	if (dma_submit_error(dmaengine_submit(dma->rx_desc))) {
+		dev_err(dev, "DMA submit failed\n");
+		return -EINVAL;
+	}
+
+	reinit_completion(&dspi->dma->cmd_rx_complete);
+	reinit_completion(&dspi->dma->cmd_tx_complete);
+
+	dma_async_issue_pending(dma->chan_rx);
+	dma_async_issue_pending(dma->chan_tx);
+
+	time_left = wait_for_completion_timeout(&dspi->dma->cmd_tx_complete,
+					DMA_COMPLETION_TIMEOUT);
+	if (time_left == 0) {
+		dev_err(dev, "DMA tx timeout\n");
+		dmaengine_terminate_all(dma->chan_tx);
+		dmaengine_terminate_all(dma->chan_rx);
+		return -ETIMEDOUT;
+	}
+
+	time_left = wait_for_completion_timeout(&dspi->dma->cmd_rx_complete,
+					DMA_COMPLETION_TIMEOUT);
+	if (time_left == 0) {
+		dev_err(dev, "DMA rx timeout\n");
+		dmaengine_terminate_all(dma->chan_tx);
+		dmaengine_terminate_all(dma->chan_rx);
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static int dspi_dma_xfer(struct fsl_dspi *dspi)
+{
+	struct fsl_dspi_dma *dma = dspi->dma;
+	struct device *dev = &dspi->pdev->dev;
+	int curr_remaining_bytes;
+	int bytes_per_buffer;
+	int tx_word;
+	int ret = 0;
+
+	tx_word = is_double_byte_mode(dspi);
+	curr_remaining_bytes = dspi->len;
+	while (curr_remaining_bytes) {
+		/* Check if current transfer fits the DMA buffer */
+		dma->curr_xfer_len = curr_remaining_bytes;
+		bytes_per_buffer = DSPI_DMA_BUFSIZE /
+				(DSPI_FIFO_SIZE / (tx_word ? 2 : 1));
+		if (curr_remaining_bytes > bytes_per_buffer)
+			dma->curr_xfer_len = bytes_per_buffer;
+
+		ret = dspi_next_xfer_dma_submit(dspi);
+		if (ret) {
+			dev_err(dev, "DMA transfer failed\n");
+			goto exit;
+
+		} else {
+			curr_remaining_bytes -= dma->curr_xfer_len;
+			if (curr_remaining_bytes < 0)
+				curr_remaining_bytes = 0;
+			dspi->len = curr_remaining_bytes;
+		}
+	}
+
+exit:
+	return ret;
+}
+
+static int dspi_request_dma(struct fsl_dspi *dspi, phys_addr_t phy_addr)
+{
+	struct fsl_dspi_dma *dma;
+	struct dma_slave_config cfg;
+	struct device *dev = &dspi->pdev->dev;
+	int ret;
+
+	dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
+	if (!dma)
+		return -ENOMEM;
+
+	dma->chan_rx = dma_request_slave_channel(dev, "rx");
+	if (!dma->chan_rx) {
+		dev_err(dev, "rx dma channel not available\n");
+		ret = -ENODEV;
+		return ret;
+	}
+
+	dma->chan_tx = dma_request_slave_channel(dev, "tx");
+	if (!dma->chan_tx) {
+		dev_err(dev, "tx dma channel not available\n");
+		ret = -ENODEV;
+		goto err_tx_channel;
+	}
+
+	dma->tx_dma_buf = dma_alloc_coherent(dev, DSPI_DMA_BUFSIZE,
+					&dma->tx_dma_phys, GFP_KERNEL);
+	if (!dma->tx_dma_buf) {
+		ret = -ENOMEM;
+		goto err_tx_dma_buf;
+	}
+
+	dma->rx_dma_buf = dma_alloc_coherent(dev, DSPI_DMA_BUFSIZE,
+					&dma->rx_dma_phys, GFP_KERNEL);
+	if (!dma->rx_dma_buf) {
+		ret = -ENOMEM;
+		goto err_rx_dma_buf;
+	}
+
+	cfg.src_addr = phy_addr + SPI_POPR;
+	cfg.dst_addr = phy_addr + SPI_PUSHR;
+	cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	cfg.src_maxburst = 1;
+	cfg.dst_maxburst = 1;
+
+	cfg.direction = DMA_DEV_TO_MEM;
+	ret = dmaengine_slave_config(dma->chan_rx, &cfg);
+	if (ret) {
+		dev_err(dev, "can't configure rx dma channel\n");
+		ret = -EINVAL;
+		goto err_slave_config;
+	}
+
+	cfg.direction = DMA_MEM_TO_DEV;
+	ret = dmaengine_slave_config(dma->chan_tx, &cfg);
+	if (ret) {
+		dev_err(dev, "can't configure tx dma channel\n");
+		ret = -EINVAL;
+		goto err_slave_config;
+	}
+
+	dspi->dma = dma;
+	init_completion(&dma->cmd_tx_complete);
+	init_completion(&dma->cmd_rx_complete);
+
+	return 0;
+
+err_slave_config:
+	devm_kfree(dev, dma->rx_dma_buf);
+err_rx_dma_buf:
+	devm_kfree(dev, dma->tx_dma_buf);
+err_tx_dma_buf:
+	dma_release_channel(dma->chan_tx);
+err_tx_channel:
+	dma_release_channel(dma->chan_rx);
+
+	devm_kfree(dev, dma);
+	dspi->dma = NULL;
+
+	return ret;
+}
+
+static void dspi_release_dma(struct fsl_dspi *dspi)
+{
+	struct fsl_dspi_dma *dma = dspi->dma;
+	struct device *dev = &dspi->pdev->dev;
+
+	if (dma) {
+		if (dma->chan_tx) {
+			dma_unmap_single(dev, dma->tx_dma_phys,
+					DSPI_DMA_BUFSIZE, DMA_TO_DEVICE);
+			dma_release_channel(dma->chan_tx);
+		}
+
+		if (dma->chan_rx) {
+			dma_unmap_single(dev, dma->rx_dma_phys,
+					DSPI_DMA_BUFSIZE, DMA_FROM_DEVICE);
+			dma_release_channel(dma->chan_rx);
+		}
+	}
+}
+
 static void hz_to_spi_baud(char *pbr, char *br, int speed_hz,
 		unsigned long clkrate)
 {
@@ -424,6 +709,12 @@ static int dspi_transfer_one_message(struct spi_master *master,
 			regmap_write(dspi->regmap, SPI_RSER, SPI_RSER_TCFQE);
 			dspi_tcfq_write(dspi);
 			break;
+		case DSPI_DMA_MODE:
+			regmap_write(dspi->regmap, SPI_RSER,
+				SPI_RSER_TFFFE | SPI_RSER_TFFFD |
+				SPI_RSER_RFDFE | SPI_RSER_RFDFD);
+			status = dspi_dma_xfer(dspi);
+			goto out;
 		default:
 			dev_err(&dspi->pdev->dev, "unsupported trans_mode %u\n",
 				trans_mode);
@@ -733,6 +1024,13 @@ static int dspi_probe(struct platform_device *pdev)
 	if (ret)
 		goto out_master_put;
 
+	if (dspi->devtype_data->trans_mode == DSPI_DMA_MODE) {
+		if (dspi_request_dma(dspi, res->start)) {
+			dev_err(&pdev->dev, "can't get dma channels\n");
+			goto out_clk_put;
+		}
+	}
+
 	master->max_speed_hz =
 		clk_get_rate(dspi->clk) / dspi->devtype_data->max_clock_factor;
 
@@ -761,6 +1059,7 @@ static int dspi_remove(struct platform_device *pdev)
 	struct fsl_dspi *dspi = spi_master_get_devdata(master);
 
 	/* Disconnect from the SPI framework */
+	dspi_release_dma(dspi);
 	clk_disable_unprepare(dspi->clk);
 	spi_unregister_master(dspi->master);
 
-- 
2.10.2