mx28: fix i.MX28 spi driver

The generic spi flash driver (drivers/mtd/spi/spi_flash.c) uses the
spi low level driver's spi_xfer() function with len=0 to deassert the
SPI flash' chip select. But the i.MX28 spi driver rejects this call
due to len=0.

This patch implements an exception for len=0 with the SPI_XFER_END
flag set. This results in an extra read with the chip select being
deasserted afterwards. There seems to be no way to deassert the signal
by hand.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>

diff --git a/drivers/spi/mxs_spi.c b/drivers/spi/mxs_spi.c
index 4c27fef..adb9ca8 100644 (file)
--- a/drivers/spi/mxs_spi.c
+++ b/drivers/spi/mxs_spi.c
@@ -129,9 +129,15 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
        int len = bitlen / 8;
        const char *tx = dout;
        char *rx = din;
-
-       if (bitlen == 0)
-               return 0;
+       char dummy;
+
+       if (bitlen == 0) {
+               if (flags & SPI_XFER_END) {
+                       rx = &dummy;
+                       len = 1;
+               } else
+                       return 0;
+       }
 
        if (!rx && !tx)
                return 0;