spi: omap2-mcspi: poll OMAP2_MCSPI_CHSTAT_RXS for PIO transfer

When running the spi-loopback-test with slower clock rate like 10 KHz,
the test for 251 bytes transfer was failed.  This failure triggered an
spi-omap2-mcspi's error message "DMA RX last word empty".

This message means that PIO for reading the remaining bytes due to the
DMA transfer length reduction is failed.  This problem can be fixed by
polling OMAP2_MCSPI_CHSTAT_RXS bit in channel status register to wait
until the receive buffer register is filled.

Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 79800e991ccd537180866aa4671ab165a4f896f8..7275223dbcd454d879bbb7a61e2ee50479212da8 100644 (file)
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -454,6 +454,8 @@ omap2_mcspi_rx_dma(struct spi_device *spi, struct spi_transfer *xfer,
        int                     elements = 0;
        int                     word_len, element_count;
        struct omap2_mcspi_cs   *cs = spi->controller_state;
+       void __iomem            *chstat_reg = cs->base + OMAP2_MCSPI_CHSTAT0;
+
        mcspi = spi_master_get_devdata(spi->master);
        mcspi_dma = &mcspi->dma_channels[spi->chip_select];
        count = xfer->len;
@@ -549,8 +551,8 @@ omap2_mcspi_rx_dma(struct spi_device *spi, struct spi_transfer *xfer,
        if (l & OMAP2_MCSPI_CHCONF_TURBO) {
                elements--;
 
-               if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
-                                  & OMAP2_MCSPI_CHSTAT_RXS)) {
+               if (!mcspi_wait_for_reg_bit(chstat_reg,
+                                           OMAP2_MCSPI_CHSTAT_RXS)) {
                        u32 w;
 
                        w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);
@@ -568,8 +570,7 @@ omap2_mcspi_rx_dma(struct spi_device *spi, struct spi_transfer *xfer,
                        return count;
                }
        }
-       if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
-                               & OMAP2_MCSPI_CHSTAT_RXS)) {
+       if (!mcspi_wait_for_reg_bit(chstat_reg, OMAP2_MCSPI_CHSTAT_RXS)) {
                u32 w;
 
                w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);