From 530b1dbd97846b110ea8a94c7cc903eca21786e5 Mon Sep 17 00:00:00 2001 From: Arturas Moskvinas Date: Fri, 1 Mar 2024 09:12:04 +0200 Subject: [PATCH] gpio: 74x164: Enable output pins after registers are reset 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#L130 [1] Link: https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L150 [2] Signed-off-by: Arturas Moskvinas Signed-off-by: Bartosz Golaszewski --- 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 e00c33310517..753e7be039e4 100644 --- a/drivers/gpio/gpio-74x164.c +++ b/drivers/gpio/gpio-74x164.c @@ -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;