3.16.84-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Linus Walleij <[email protected]> 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 <[email protected]> Reported-by: Mark Brown <[email protected]> Signed-off-by: Linus Walleij <[email protected]> Reviewed-by: Mark Brown <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Ulf Hansson <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- drivers/mmc/host/mmc_spi.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/drivers/mmc/host/mmc_spi.c +++ b/drivers/mmc/host/mmc_spi.c @@ -1149,17 +1149,22 @@ static void mmc_spi_initsequence(struct * 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,
