4.19-stable review patch. If anyone has any objections, please let me know.
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From: Arturas Moskvinas arturas.moskvinas@gmail.com
[ Upstream commit 530b1dbd97846b110ea8a94c7cc903eca21786e5 ]
Chip outputs are enabled[1] before actual reset is performed[2] which might cause pin output value to flip flop if previous pin value was set to 1. Fix that behavior by making sure chip is fully reset before all outputs are enabled.
Flip-flop can be noticed when module is removed and inserted again and one of the pins was changed to 1 before removal. 100 microsecond flipping is noticeable on oscilloscope (100khz SPI bus).
For a properly reset chip - output is enabled around 100 microseconds (on 100khz SPI bus) later during probing process hence should be irrelevant behavioral change.
Fixes: 7ebc194d0fd4 (gpio: 74x164: Introduce 'enable-gpios' property) Link: https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L1... [1] Link: https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L1... [2] Signed-off-by: Arturas Moskvinas arturas.moskvinas@gmail.com Signed-off-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpio/gpio-74x164.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpio-74x164.c b/drivers/gpio/gpio-74x164.c index fb7b620763a25..a47897f2a83de 100644 --- a/drivers/gpio/gpio-74x164.c +++ b/drivers/gpio/gpio-74x164.c @@ -132,8 +132,6 @@ static int gen_74x164_probe(struct spi_device *spi) if (IS_ERR(chip->gpiod_oe)) return PTR_ERR(chip->gpiod_oe);
- gpiod_set_value_cansleep(chip->gpiod_oe, 1); - spi_set_drvdata(spi, chip);
chip->gpio_chip.label = spi->modalias; @@ -158,6 +156,8 @@ static int gen_74x164_probe(struct spi_device *spi) goto exit_destroy; }
+ gpiod_set_value_cansleep(chip->gpiod_oe, 1); + ret = gpiochip_add_data(&chip->gpio_chip, chip); if (!ret) return 0;