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Subject[PATCH AUTOSEL for-4.9 04/53] spi: imx: adjust watermark level according to transfer length
Date
From: Jiada Wang <jiada_wang@mentor.com>

[ Upstream commit 66459c5a50a787c474b734b586328f7111ab6df0 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.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 deb782f6556c..84a2b152be55 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -210,7 +210,7 @@ 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;
@@ -227,12 +227,16 @@ 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;
}

@@ -818,10 +822,6 @@ 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
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