| From af3ed119329cf9690598c5a562d95dfd128e91d6 Mon Sep 17 00:00:00 2001 |
| From: Linus Walleij <linus.walleij@linaro.org> |
| Date: Wed, 4 Dec 2019 16:27:49 +0100 |
| Subject: mmc: spi: Toggle SPI polarity, do not hardcode it |
| |
| From: Linus Walleij <linus.walleij@linaro.org> |
| |
| 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> |
| |
| --- |
| 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 |
| @@ -1154,17 +1154,22 @@ 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, |
