Commit 73412b7f authored by Arturas Moskvinas's avatar Arturas Moskvinas Committed by sanglipeng1
Browse files

gpio: 74x164: Enable output pins after registers are reset 

stable inclusion
from stable-v5.10.212
commit 947baae18505e4341a7a7d923d3c0f0557b85559
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAGOP2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=947baae18505e4341a7a7d923d3c0f0557b85559

--------------------------------

[ 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: 7ebc194d (gpio: 74x164: Introduce 'enable-gpios' property)
Link: https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L130 [1]
Link: https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L150

 [2]
Signed-off-by: default avatarArturas Moskvinas <arturas.moskvinas@gmail.com>
Signed-off-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarsanglipeng1 <sanglipeng1@jd.com>
parent 172cfa0f

drivers/gpio/gpio-74x164.c

+2 −2
Original line number Diff line number Diff line
@@ -127,8 +127,6 @@ 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;
@@ -153,6 +151,8 @@ 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;