atmel_spi: reload RCR before TCR

We have a wifi module connected to the spi bus and got sometimes FIFO
overrun errors on the spi bus.

After some investigation i found that the driver loads the TCR (transmit
count) register before the RCR (receive count).  When the transfer list is
not empty the atmel_spi_next_message is called while tx and rx are enabled.
 As soon as the TCR is loaded, hardware starts transfer and causes a rx
fifo overrun because the RCR is not loaded yet.

Load the RCR before the TCR.  After this patch the fifo overrun disapears
at out setup.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Rini van Zetten <rini@arvoo.nl>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index ff6a14bf128007d268eedf6bb999a89227d00f05..ff10808183a36f4e9d642469e42653d50f13ca24 100644 (file)
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -195,8 +195,8 @@ static void atmel_spi_next_xfer(struct spi_master *master,
                xfer, xfer->len, xfer->tx_buf, xfer->tx_dma,
                xfer->rx_buf, xfer->rx_dma, spi_readl(as, IMR));
 
-       spi_writel(as, TCR, len);
        spi_writel(as, RCR, len);
+       spi_writel(as, TCR, len);
        spi_writel(as, PTCR, SPI_BIT(TXTEN) | SPI_BIT(RXTEN));
 }