commit 7f61257 upstream.

Add a software PWM which toggles a GPIO from a high-resolution timer.

This will naturally not be as accurate or as efficient as a hardware
PWM, but it is useful in some cases.  I have for example used it for
evaluating LED brightness handling (via leds-pwm) on a board where the
LED was just hooked up to a GPIO, and for a simple verification of the
timer frequency on another platform.

Since high-resolution timers are used, sleeping GPIO chips are not
supported and are rejected in the probe function.

Signed-off-by: Vincent Whitchurch <[email protected]>
Co-developed-by: Stefan Wahren <[email protected]>
Signed-off-by: Stefan Wahren <[email protected]>
Co-developed-by: Linus Walleij <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
Reviewed-by: Dhruva Gole <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Uwe Kleine-König <[email protected]>
Signed-off-by: Tim Gover <[email protected]>

pwm: Backport pwm-gpio.c to rpi-6.6.y

Enable the PWM GPIO module in Raspberry Pi kernels.

Signed-off-by: Tim Gover <[email protected]>

Signed-off-by: Tim Gover <[email protected]>