On Tue, Nov 05, 2024 at 04:39:38PM +0200, Andy Shevchenko wrote: > On Tue, Nov 05, 2024 at 12:45:23PM +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 > > $ 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 > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> Does this need to be applied, Bart? Seems it is missed in your branches... -- With Best Regards, Andy Shevchenko
