diff options
| author | Sai Kumar Cholleti <skmr537@gmail.com> | 2024-11-05 08:15:23 +0100 |
|---|---|---|
| committer | Bartosz Golaszewski <bartosz.golaszewski@linaro.org> | 2024-11-21 09:08:47 +0100 |
| commit | 72cef64180de04a7b055b4773c138d78f4ebdb77 (patch) | |
| tree | 73b992b281932e461b5e0608bc0de761f6c6a356 /drivers/gpio | |
| parent | gpio: altera: Add missed base and label initialisations (diff) | |
| download | linux-72cef64180de04a7b055b4773c138d78f4ebdb77.tar.xz linux-72cef64180de04a7b055b4773c138d78f4ebdb77.zip | |
gpio: exar: set value when external pull-up or pull-down is present
Setting GPIO direction = high, sometimes results in GPIO value = 0.
If a GPIO is pulled high, the following construction results in the
value being 0 when the desired value is 1:
$ echo "high" > /sys/class/gpio/gpio336/direction
$ cat /sys/class/gpio/gpio336/value
0
Before the GPIO direction is changed from an input to an output,
exar_set_value() is called with value = 1, but since the GPIO is an
input when exar_set_value() is called, _regmap_update_bits() reads a 1
due to an external pull-up. regmap_set_bits() sets force_write =
false, so the value (1) is not written. When the direction is then
changed, the GPIO becomes an output with the value of 0 (the hardware
default).
regmap_write_bits() sets force_write = true, so the value is always
written by exar_set_value() and an external pull-up doesn't affect the
outcome of setting direction = high.
The same can happen when a GPIO is pulled low, but the scenario is a
little more complicated.
$ echo high > /sys/class/gpio/gpio351/direction
$ cat /sys/class/gpio/gpio351/value
1
$ echo in > /sys/class/gpio/gpio351/direction
$ cat /sys/class/gpio/gpio351/value
0
$ echo low > /sys/class/gpio/gpio351/direction
$ cat /sys/class/gpio/gpio351/value
1
Fixes: 36fb7218e878 ("gpio: exar: switch to using regmap")
Co-developed-by: Matthew McClain <mmcclain@noprivs.com>
Signed-off-by: Matthew McClain <mmcclain@noprivs.com>
Signed-off-by: Sai Kumar Cholleti <skmr537@gmail.com>
Cc: stable@vger.kernel.org
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20241105071523.2372032-1-skmr537@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Diffstat (limited to 'drivers/gpio')
| -rw-r--r-- | drivers/gpio/gpio-exar.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/gpio/gpio-exar.c b/drivers/gpio/gpio-exar.c index 5170fe7599cd..d5909a4f0433 100644 --- a/drivers/gpio/gpio-exar.c +++ b/drivers/gpio/gpio-exar.c @@ -99,11 +99,13 @@ static void exar_set_value(struct gpio_chip *chip, unsigned int offset, struct exar_gpio_chip *exar_gpio = gpiochip_get_data(chip); unsigned int addr = exar_offset_to_lvl_addr(exar_gpio, offset); unsigned int bit = exar_offset_to_bit(exar_gpio, offset); + unsigned int bit_value = value ? BIT(bit) : 0; - if (value) - regmap_set_bits(exar_gpio->regmap, addr, BIT(bit)); - else - regmap_clear_bits(exar_gpio->regmap, addr, BIT(bit)); + /* + * regmap_write_bits() forces value to be written when an external + * pull up/down might otherwise indicate value was already set. + */ + regmap_write_bits(exar_gpio->regmap, addr, BIT(bit), bit_value); } static int exar_direction_output(struct gpio_chip *chip, unsigned int offset, |