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 <[email protected]>
Signed-off-by: Matthew McClain <[email protected]>
Signed-off-by: Sai Kumar Cholleti <[email protected]>
Cc: [email protected]
Reviewed-by: Andy Shevchenko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Bartosz Golaszewski <[email protected]>

0 files changed, 0 insertions, 0 deletions