pwm: Add ChromeOS EC PWM driver
Use the new ChromeOS EC EC_CMD_PWM_{GET,SET}_DUTY commands to control
one or more PWMs attached to the Embedded Controller. Because the EC
allows us to modify the duty cycle (as a percentage, where U16_MAX is
100%) but not the period, we assign the period a fixed value of
EC_PWM_MAX_DUTY and reject all attempts to change it.
This driver supports only device tree at the moment, because that
provides a very flexible way of describing the relationship between PWMs
and their consumer devices (e.g., backlight). On a non-DT system, we'll
probably want to use the non-GENERIC addressing (i.e., we'll need to
make special device instances that will use EC_PWM_TYPE_KB_LIGHT or
EC_PWM_TYPE_DISPLAY_LIGHT), as well as the relatively inflexible
pwm_lookup infrastructure for matching devices. Defer that work for now.
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 98ae3cb..feef1dd 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -12,6 +12,7 @@
obj-$(CONFIG_PWM_BRCMSTB) += pwm-brcmstb.o
obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o
obj-$(CONFIG_PWM_CRC) += pwm-crc.o
+obj-$(CONFIG_PWM_CROS_EC) += pwm-cros-ec.o
obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o
obj-$(CONFIG_PWM_FSL_FTM) += pwm-fsl-ftm.o
obj-$(CONFIG_PWM_IMG) += pwm-img.o
