Patchwork [U-Boot] mx28: fix i.MX28 spi driver

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Submitter Fabio Estevam
Date Jan. 14, 2012, 6:53 p.m.
Message ID <CAOMZO5CGYe8tJRN6fXXQxqrWtMj71_VkETLE+pTjgQZKsyoOrA@mail.gmail.com>
Download mbox | patch
Permalink /patch/136097/
State Changes Requested
Headers show

Comments

Fabio Estevam - Jan. 14, 2012, 6:53 p.m.
On Sat, Jan 14, 2012 at 4:46 PM, Fabio Estevam <festevam@gmail.com> wrote:
> 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)?

Actually I meant this:

Patch

--- a/drivers/spi/mxs_spi.c
+++ b/drivers/spi/mxs_spi.c
@@ -136,7 +136,7 @@  int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
        if (!rx && !tx)
                return 0;

-       if (flags & SPI_XFER_BEGIN)
+       if ((flags & SPI_XFER_BEGIN) && len)
                mxs_spi_start_xfer(ssp_regs);

        while (len--) {