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mmc: spi: Toggle SPI polarity, do not hardcode it

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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
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Linus Walleij 2019-12-04 16:27:49 +01:00 committed by Ulf Hansson
parent 3976656d67
commit af3ed11932
1 changed files with 8 additions and 3 deletions
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11
drivers/mmc/host/mmc_spi.c
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@ -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,