On Mon, Nov 04, 2024 at 09:17:57PM +0530, Sai Kumar Cholleti wrote:
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
This...
$ cat /sys/class/gpio/gpio351/value 1
$ echo in > /sys/class/gpio/gpio351/direction
...this...
$ cat /sys/class/gpio/gpio351/value 0
$ echo low > /sys/class/gpio/gpio351/direction
...this...
$ cat /sys/class/gpio/gpio351/value 1
Fixes: 36fb7218e878 ("gpio: exar: switch to using regmap")
...and this lines have a trailing space.
Signed-off-by: Sai Kumar Cholleti skmr537@gmail.com Signed-off-by: Matthew McClain mmcclain@noprivs.com
Hmm... Missing Co-developed-by? This SoB chain puzzles me a bit, the committer should go last AFAIR.
...
- /*
* regmap_write_bits forces value to be written when an external
regmap_write_bits()
* pull up/down might otherwise indicate value was already set
Missing period at the end.
*/
...
Other than above LGTM.