Commit ef23fb57 authored Dec 04, 2019 by Linus Walleij Committed by Greg Kroah-Hartman Feb 11, 2020

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


Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent ff949bbf

drivers/mmc/host/mmc_spi.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -1154,17 +1154,22 @@ 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,