Commit 1b9ee288 authored by Alper Nebi Yasak's avatar Alper Nebi Yasak Committed by Anatolij Gustschin
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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: default avatarAlper Nebi Yasak <>
Reviewed-by: Simon Glass's avatarSimon Glass <>
parent fefa713b
PWM controlled by ChromeOS EC
Google's ChromeOS EC PWM is a simple PWM attached to the Embedded Controller
(EC) and controlled via a host-command interface.
An EC PWM node should be only found as a sub-node of the EC node (see
Required properties:
- compatible: Must contain "google,cros-ec-pwm"
- #pwm-cells: Should be 1. The cell specifies the PWM index.
cros-ec@0 {
compatible = "google,cros-ec-spi";
cros_ec_pwm: ec-pwm {
compatible = "google,cros-ec-pwm";
#pwm-cells = <1>;
......@@ -1170,6 +1170,23 @@ int cros_ec_battery_cutoff(struct udevice *dev, uint8_t flags)
return 0;
int cros_ec_set_pwm_duty(struct udevice *dev, uint8_t index, uint16_t duty)
struct ec_params_pwm_set_duty p;
int ret;
p.duty = duty;
p.pwm_type = EC_PWM_TYPE_GENERIC;
p.index = index;
ret = ec_command(dev, EC_CMD_PWM_SET_DUTY, 0, &p, sizeof(p),
NULL, 0);
if (ret < 0)
return ret;
return 0;
int cros_ec_set_ldo(struct udevice *dev, uint8_t index, uint8_t state)
struct ec_params_ldo_set params;
......@@ -9,6 +9,15 @@ config DM_PWM
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
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
bool "Enable support for the Exynos PWM"
depends on DM_PWM
......@@ -10,6 +10,7 @@
obj-$(CONFIG_DM_PWM) += pwm-uclass.o
obj-$(CONFIG_PWM_CROS_EC) += cros_ec_pwm.o
obj-$(CONFIG_PWM_EXYNOS) += exynos_pwm.o
obj-$(CONFIG_PWM_IMX) += pwm-imx.o pwm-imx-util.o
obj-$(CONFIG_PWM_MESON) += pwm-meson.o
// SPDX-License-Identifier: GPL-2.0+
#include <common.h>
#include <cros_ec.h>
#include <dm.h>
#include <errno.h>
#include <log.h>
#include <pwm.h>
struct cros_ec_pwm_priv {
bool enabled;
uint duty;
static int cros_ec_pwm_set_config(struct udevice *dev, uint channel,
uint period_ns, uint duty_ns)
struct cros_ec_pwm_priv *priv = dev_get_priv(dev);
uint duty;
int ret;
debug("%s: period_ns=%u, duty_ns=%u asked\n", __func__,
period_ns, duty_ns);
/* No way to set the period, only a relative duty cycle */
duty = EC_PWM_MAX_DUTY * duty_ns / period_ns;
if (duty > EC_PWM_MAX_DUTY)
if (!priv->enabled) {
priv->duty = duty;
debug("%s: duty=%#x to-be-set\n", __func__, duty);
return 0;
ret = cros_ec_set_pwm_duty(dev->parent, channel, duty);
if (ret) {
debug("%s: duty=%#x failed\n", __func__, duty);
return ret;
priv->duty = duty;
debug("%s: duty=%#x set\n", __func__, duty);
return 0;
static int cros_ec_pwm_set_enable(struct udevice *dev, uint channel,
bool enable)
struct cros_ec_pwm_priv *priv = dev_get_priv(dev);
int ret;
ret = cros_ec_set_pwm_duty(dev->parent, channel,
enable ? priv->duty : 0);
if (ret) {
debug("%s: enable=%d failed\n", __func__, enable);
return ret;
priv->enabled = enable;
debug("%s: enable=%d (duty=%#x) set\n", __func__,
enable, priv->duty);
return 0;
static const struct pwm_ops cros_ec_pwm_ops = {
.set_config = cros_ec_pwm_set_config,
.set_enable = cros_ec_pwm_set_enable,
static const struct udevice_id cros_ec_pwm_ids[] = {
{ .compatible = "google,cros-ec-pwm" },
{ }
U_BOOT_DRIVER(cros_ec_pwm) = {
.name = "cros_ec_pwm",
.of_match = cros_ec_pwm_ids,
.ops = &cros_ec_pwm_ops,
.priv_auto_alloc_size = sizeof(struct cros_ec_pwm_priv),
......@@ -512,6 +512,19 @@ int cros_ec_efs_verify(struct udevice *dev, enum ec_flash_region region);
int cros_ec_battery_cutoff(struct udevice *dev, uint8_t flags);
* cros_ec_set_pwm_duty() - Set duty cycle of a generic pwm
* Note that duty value needs to be passed to the EC as a 16 bit number
* for increased precision.
* @param dev CROS-EC device
* @param index Index of the pwm
* @param duty Desired duty cycle, in 0..EC_PWM_MAX_DUTY range.
* @return 0 if OK, -ve on error
int cros_ec_set_pwm_duty(struct udevice *dev, uint8_t index, uint16_t duty);
* cros_ec_read_limit_power() - Check if power is limited by batter/charger
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