Patch "gpio: 74x164: Enable output pins after registers are reset" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gpio-74x164-enable-output-pins-after-registers-are-r.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 367f3f442e8ce057425497ac08510bf8e5a6eb4b
Author: Arturas Moskvinas <arturas.moskvinas@xxxxxxxxx>
Date:   Fri Mar 1 09:12:04 2024 +0200

    gpio: 74x164: Enable output pins after registers are reset
    
    [ 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#L130 [1]
    Link: https://elixir.bootlin.com/linux/v6.7.4/source/drivers/gpio/gpio-74x164.c#L150 [2]
    Signed-off-by: Arturas Moskvinas <arturas.moskvinas@xxxxxxxxx>
    Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpio/gpio-74x164.c b/drivers/gpio/gpio-74x164.c
index 4a55cdf089d62..ebfa0a8e57dec 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;