Hi Matthias,
On Sat, Jan 14, 2012 at 10:25 AM, Matthias Fuchs matthias.fuchs@esd.eu wrote:
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
What about the approach bellow (untested)?
--- a/drivers/spi/mxs_spi.c +++ b/drivers/spi/mxs_spi.c @@ -126,17 +126,14 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, { struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave); struct mx28_ssp_regs *ssp_regs = mxs_slave->regs; - int len = bitlen / 8; + unsigned int len = bitlen / 8; const char *tx = dout; char *rx = din;
- if (bitlen == 0) - return 0; - if (!rx && !tx) return 0;
- if (flags & SPI_XFER_BEGIN) + if ((flags & SPI_XFER_BEGIN) && !len) mxs_spi_start_xfer(ssp_regs);
while (len--) {