On Wed, 4 Dec 2019 at 16:29, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>
> The code in mmc_spi_initsequence() tries to send a burst with
> high chipselect and for this reason hardcodes the device into
> SPI_CS_HIGH.
>
> This is not good because the SPI_CS_HIGH flag indicates
> logical "asserted" CS not always the physical level. In
> some cases the signal is inverted in the GPIO library and
> in that case SPI_CS_HIGH is already set, and enforcing
> SPI_CS_HIGH again will actually drive it low.
>
> Instead of hard-coding this, toggle the polarity so if the
> default is LOW it goes high to assert chipselect but if it
> is already high then toggle it low instead.
>
> Cc: Phil Elwell <phil@xxxxxxxxxxxxxxx>
> Reported-by: Mark Brown <broonie@xxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Seems like we should add a stable tag, right?
In any case, I have applied this for next to let it cook for a while, thanks!
Kind regards
Uffe
> ---
> drivers/mmc/host/mmc_spi.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
> index 74c6cfbf9172..1f02f54f09c0 100644
> --- a/drivers/mmc/host/mmc_spi.c
> +++ b/drivers/mmc/host/mmc_spi.c
> @@ -1134,17 +1134,22 @@ static void mmc_spi_initsequence(struct mmc_spi_host *host)
> * SPI protocol. Another is that when chipselect is released while
> * the card returns BUSY status, the clock must issue several cycles
> * with chipselect high before the card will stop driving its output.
> + *
> + * SPI_CS_HIGH means "asserted" here. In some cases like when using
> + * GPIOs for chip select, SPI_CS_HIGH is set but this will be logically
> + * inverted by gpiolib, so if we want to ascertain to drive it high
> + * we should toggle the default with an XOR as we do here.
> */
> - host->spi->mode |= SPI_CS_HIGH;
> + host->spi->mode ^= SPI_CS_HIGH;
> if (spi_setup(host->spi) != 0) {
> /* Just warn; most cards work without it. */
> dev_warn(&host->spi->dev,
> "can't change chip-select polarity\n");
> - host->spi->mode &= ~SPI_CS_HIGH;
> + host->spi->mode ^= SPI_CS_HIGH;
> } else {
> mmc_spi_readbytes(host, 18);
>
> - host->spi->mode &= ~SPI_CS_HIGH;
> + host->spi->mode ^= SPI_CS_HIGH;
> if (spi_setup(host->spi) != 0) {
> /* Wot, we can't get the same setup we had before? */
> dev_err(&host->spi->dev,
> --
> 2.23.0
>
