pwm: Add a driver for Chrome OS EC PWM
This PWM is used in rk3399-gru-bob and rk3399-gru-kevin to control
the display brightness. We can only change the duty cycle, so on
set_config() we just try to match the duty cycle that dividing duty_ns
by period_ns gives us. To disable, we set the duty cycle to zero while
keeping the old value for when we want to re-enable it.
The cros_ec_set_pwm_duty() function is taken from Depthcharge's
cros_ec_set_bl_pwm_duty() but modified to use the generic pwm type.
The driver itself is very loosely based on rk_pwm.c for the general pwm
driver structure.
The devicetree binding file is from Linux, before it was converted to
YAML at 5df5a577a6b4 ("dt-bindings: pwm: Convert google,cros-ec-pwm.txt
to YAML format") in their repo.
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index ccf81ab..cf7f4c6 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -9,6 +9,15 @@
frequency/period can be controlled along with the proportion of that
time that the signal is high.
+config PWM_CROS_EC
+ bool "Enable support for the Chrome OS EC PWM"
+ depends on DM_PWM
+ help
+ This PWM is found on several Chrome OS devices and controlled by
+ the Chrome OS embedded controller. It may be used to control the
+ screen brightness and/or the keyboard backlight depending on the
+ device.
+
config PWM_EXYNOS
bool "Enable support for the Exynos PWM"
depends on DM_PWM