[PATCH] Revert "spi: omap2-mcspi: Set FIFO DMA trigger level to word length"

[David Lechner]

This reverts commit b682cffa3ac6d9d9e16e9b413c45caee3b391fab.

That commit breaks displays using tinydrm drivers, such as ili9225.

It causes corruption in the image that is displayed (it looks like only
1/2 of the framebuffer data is sent, the other half of the display
remains blank.)

The following error appears multiple times:

    ili9225 spi1.0: EOW timed out

Eventually, the system locks up without any additional errors.

Cc: Vignesh R <vigne...@ti.com>
Signed-off-by: David Lechner <da...@lechnology.com>
---
 drivers/spi/spi-omap2-mcspi.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 2fd8881fcd65..5a3854ff2e08 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -306,7 +306,7 @@ static void omap2_mcspi_set_fifo(const struct spi_device 
*spi,
        struct omap2_mcspi_cs *cs = spi->controller_state;
        struct omap2_mcspi *mcspi;
        unsigned int wcnt;
-       int max_fifo_depth, bytes_per_word;
+       int max_fifo_depth, fifo_depth, bytes_per_word;
        u32 chconf, xferlevel;
 
        mcspi = spi_master_get_devdata(master);
@@ -322,6 +322,10 @@ static void omap2_mcspi_set_fifo(const struct spi_device 
*spi,
                else
                        max_fifo_depth = OMAP2_MCSPI_MAX_FIFODEPTH;
 
+               fifo_depth = gcd(t->len, max_fifo_depth);
+               if (fifo_depth < 2 || fifo_depth % bytes_per_word != 0)
+                       goto disable_fifo;
+
                wcnt = t->len / bytes_per_word;
                if (wcnt > OMAP2_MCSPI_MAX_FIFOWCNT)
                        goto disable_fifo;
@@ -329,17 +333,16 @@ static void omap2_mcspi_set_fifo(const struct spi_device 
*spi,
                xferlevel = wcnt << 16;
                if (t->rx_buf != NULL) {
                        chconf |= OMAP2_MCSPI_CHCONF_FFER;
-                       xferlevel |= (bytes_per_word - 1) << 8;
+                       xferlevel |= (fifo_depth - 1) << 8;
                }
-
                if (t->tx_buf != NULL) {
                        chconf |= OMAP2_MCSPI_CHCONF_FFET;
-                       xferlevel |= bytes_per_word - 1;
+                       xferlevel |= fifo_depth - 1;
                }
 
                mcspi_write_reg(master, OMAP2_MCSPI_XFERLEVEL, xferlevel);
                mcspi_write_chconf0(spi, chconf);
-               mcspi->fifo_depth = max_fifo_depth;
+               mcspi->fifo_depth = fifo_depth;
 
                return;
        }
@@ -598,6 +601,7 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct 
spi_transfer *xfer)
        struct dma_slave_config cfg;
        enum dma_slave_buswidth width;
        unsigned es;
+       u32                     burst;
        void __iomem            *chstat_reg;
        void __iomem            *irqstat_reg;
        int                     wait_res;
@@ -617,14 +621,22 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct 
spi_transfer *xfer)
        }
 
        count = xfer->len;
+       burst = 1;
+
+       if (mcspi->fifo_depth > 0) {
+               if (count > mcspi->fifo_depth)
+                       burst = mcspi->fifo_depth / es;
+               else
+                       burst = count / es;
+       }
 
        memset(&cfg, 0, sizeof(cfg));
        cfg.src_addr = cs->phys + OMAP2_MCSPI_RX0;
        cfg.dst_addr = cs->phys + OMAP2_MCSPI_TX0;
        cfg.src_addr_width = width;
        cfg.dst_addr_width = width;
-       cfg.src_maxburst = es;
-       cfg.dst_maxburst = es;
+       cfg.src_maxburst = burst;
+       cfg.dst_maxburst = burst;
 
        rx = xfer->rx_buf;
        tx = xfer->tx_buf;
-- 
2.17.1