[PATCH 1/1] spi: imx: adjust watermark level according to transfer length

[PATCH 1/1] spi: imx: adjust watermark level according to transfer length

[jiada_wang]

From: Jiada Wang <jiada_wang@mentor.com>

Previously DMA watermark level is configured to fifosize/2,
DMA mode can be used only when transfer length can be divided
by 'watermark level * bpw', which makes DMA mode not pratical.

This patch adjusts watermark level to largest number (no bigger
than fifosize/2) which can divide 'tranfer length / bpw' for
each transfer.

Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
---
 drivers/spi/spi-imx.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 32ced64..9a7c62f 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -211,7 +211,7 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 			 struct spi_transfer *transfer)
 {
 	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
-	unsigned int bpw;
+	unsigned int bpw, i;
 
 	if (!master->dma_rx)
 		return false;
@@ -228,12 +228,16 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 	if (bpw != 1 && bpw != 2 && bpw != 4)
 		return false;
 
-	if (transfer->len < spi_imx->wml * bpw)
-		return false;
+	for (i = spi_imx_get_fifosize(spi_imx) / 2; i > 0; i--) {
+		if (!(transfer->len % (i * bpw)))
+			break;
+	}
 
-	if (transfer->len % (spi_imx->wml * bpw))
+	if (i == 0)
 		return false;
 
+	spi_imx->wml = i;
+
 	return true;
 }
 
@@ -837,10 +841,6 @@ static int spi_imx_dma_configure(struct spi_master *master,
 	struct dma_slave_config rx = {}, tx = {};
 	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
 
-	if (bytes_per_word == spi_imx->bytes_per_word)
-		/* Same as last time */
-		return 0;
-
 	switch (bytes_per_word) {
 	case 4:
 		buswidth = DMA_SLAVE_BUSWIDTH_4_BYTES;
-- 
2.7.4

Applied "spi: imx: adjust watermark level according to transfer length" to the spi tree

[Mark Brown]

The patch

   spi: imx: adjust watermark level according to transfer length

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 66459c5a50a787c474b734b586328f7111ab6df0 Mon Sep 17 00:00:00 2001
From: Jiada Wang <jiada_wang@mentor.com>
Date: Fri, 6 Jan 2017 04:22:18 -0800
Subject: [PATCH] spi: imx: adjust watermark level according to transfer length

Previously DMA watermark level is configured to fifosize/2,
DMA mode can be used only when transfer length can be divided
by 'watermark level * bpw', which makes DMA mode not pratical.

This patch adjusts watermark level to largest number (no bigger
than fifosize/2) which can divide 'tranfer length / bpw' for
each transfer.

Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-imx.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 32ced64a5bb9..9a7c62f471dc 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -211,7 +211,7 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 			 struct spi_transfer *transfer)
 {
 	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
-	unsigned int bpw;
+	unsigned int bpw, i;
 
 	if (!master->dma_rx)
 		return false;
@@ -228,12 +228,16 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
 	if (bpw != 1 && bpw != 2 && bpw != 4)
 		return false;
 
-	if (transfer->len < spi_imx->wml * bpw)
-		return false;
+	for (i = spi_imx_get_fifosize(spi_imx) / 2; i > 0; i--) {
+		if (!(transfer->len % (i * bpw)))
+			break;
+	}
 
-	if (transfer->len % (spi_imx->wml * bpw))
+	if (i == 0)
 		return false;
 
+	spi_imx->wml = i;
+
 	return true;
 }
 
@@ -837,10 +841,6 @@ static int spi_imx_dma_configure(struct spi_master *master,
 	struct dma_slave_config rx = {}, tx = {};
 	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
 
-	if (bytes_per_word == spi_imx->bytes_per_word)
-		/* Same as last time */
-		return 0;
-
 	switch (bytes_per_word) {
 	case 4:
 		buswidth = DMA_SLAVE_BUSWIDTH_4_BYTES;
-- 
2.11.0