diff options
| author | Linus Walleij <linus.walleij@linaro.org> | 2019-12-04 16:27:49 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2020-05-22 21:19:16 +0100 |
| commit | d525915ba099d34e08606ef44bf8cdc899c18f95 (patch) | |
| tree | 8dc661a2bfc583eec3cdef05fc7564a9c971928f | |
| parent | 523433150b46ea50e434a32909554e11d7b215b5 (diff) | |
| download | linux-stable-d525915ba099d34e08606ef44bf8cdc899c18f95.tar.gz | |
mmc: spi: Toggle SPI polarity, do not hardcode it
commit af3ed119329cf9690598c5a562d95dfd128e91d6 upstream.
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@raspberrypi.org>
Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20191204152749.12652-1-linus.walleij@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | drivers/mmc/host/mmc_spi.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c index a55c4fb42b002..cf1e58b735607 100644 --- a/drivers/mmc/host/mmc_spi.c +++ b/drivers/mmc/host/mmc_spi.c @@ -1149,17 +1149,22 @@ 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, |