[PATCH 5.4 085/309] mmc: spi: Toggle SPI polarity, do not hardcode it
From: Greg Kroah-Hartman
Date: Mon Feb 10 2020 - 08:10:48 EST
From: Linus Walleij <linus.walleij@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Reported-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Reviewed-by: Mark Brown <broonie@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20191204152749.12652-1-linus.walleij@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -1134,17 +1134,22 @@ 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,