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>

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 32ced64a5bb9a012e2edd0d415d8c477ebc0522a..9a7c62f471dc8cb2e62638d2846989da076442ae 100644 (file)
--- 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;