Applied "spi: spi-fsl-dspi: Fix incorrect DMA setup" to the spi tree

[Mark Brown]

The patch

   spi: spi-fsl-dspi: Fix incorrect DMA setup

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 1eaccf210c59e04eb6e9b5469a60d6609c95ac61 Mon Sep 17 00:00:00 2001
From: Sanchayan Maity <maitysanchayan at gmail.com>
Date: Tue, 22 Nov 2016 12:31:30 +0530
Subject: [PATCH] spi: spi-fsl-dspi: Fix incorrect DMA setup

Currently dmaengine_prep_slave_single was being called with length
set to the complete DMA buffer size. This resulted in unwanted bytes
being transferred to the SPI register leading to clock and MOSI lines
having unwanted data even after chip select got deasserted and the
required bytes having been transferred.

While at it also clean up the use of curr_xfer_len which is central
to the DMA setup, from bytes to DMA transfers for every use.

Signed-off-by: Sanchayan Maity <maitysanchayan at gmail.com>
Reviewed-by: Stefan Agner <stefan at agner.ch>
Signed-off-by: Mark Brown <broonie at kernel.org>
---
 drivers/spi/spi-fsl-dspi.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 22f7ce1279bd..cb41c327bd77 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -151,6 +151,7 @@ static const struct fsl_dspi_devtype_data ls2085a_data = {
 };
 
 struct fsl_dspi_dma {
+	/* Length of transfer in words of DSPI_FIFO_SIZE */
 	u32 curr_xfer_len;
 
 	u32 *tx_dma_buf;
@@ -217,15 +218,13 @@ 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;
+	int i;
 	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++) {
+		for (i = 0; i < dma->curr_xfer_len; i++) {
 			d = dspi->dma->rx_dma_buf[i];
 			rx_word ? (*(u16 *)dspi->rx = d) :
 						(*(u8 *)dspi->rx = d);
@@ -242,14 +241,12 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
 	struct device *dev = &dspi->pdev->dev;
 	int time_left;
 	int tx_word;
-	int i, len;
+	int i;
 	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++) {
+	for (i = 0; i < dma->curr_xfer_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) |
@@ -265,7 +262,9 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
 
 	dma->tx_desc = dmaengine_prep_slave_single(dma->chan_tx,
 					dma->tx_dma_phys,
-					DSPI_DMA_BUFSIZE, DMA_MEM_TO_DEV,
+					dma->curr_xfer_len *
+					DMA_SLAVE_BUSWIDTH_4_BYTES,
+					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");
@@ -281,7 +280,9 @@ static int dspi_next_xfer_dma_submit(struct fsl_dspi *dspi)
 
 	dma->rx_desc = dmaengine_prep_slave_single(dma->chan_rx,
 					dma->rx_dma_phys,
-					DSPI_DMA_BUFSIZE, DMA_DEV_TO_MEM,
+					dma->curr_xfer_len *
+					DMA_SLAVE_BUSWIDTH_4_BYTES,
+					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");
@@ -328,17 +329,17 @@ static int dspi_dma_xfer(struct fsl_dspi *dspi)
 	struct device *dev = &dspi->pdev->dev;
 	int curr_remaining_bytes;
 	int bytes_per_buffer;
-	int tx_word;
+	int word = 1;
 	int ret = 0;
 
-	tx_word = is_double_byte_mode(dspi);
+	if (is_double_byte_mode(dspi))
+		word = 2;
 	curr_remaining_bytes = dspi->len;
+	bytes_per_buffer = DSPI_DMA_BUFSIZE / DSPI_FIFO_SIZE;
 	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 = curr_remaining_bytes / word;
+		if (dma->curr_xfer_len > bytes_per_buffer)
 			dma->curr_xfer_len = bytes_per_buffer;
 
 		ret = dspi_next_xfer_dma_submit(dspi);
@@ -347,7 +348,7 @@ static int dspi_dma_xfer(struct fsl_dspi *dspi)
 			goto exit;
 
 		} else {
-			curr_remaining_bytes -= dma->curr_xfer_len;
+			curr_remaining_bytes -= dma->curr_xfer_len * word;
 			if (curr_remaining_bytes < 0)
 				curr_remaining_bytes = 0;
 			dspi->len = curr_remaining_bytes;
-- 
2.10.2