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>

1 files 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;