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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: Alper Nebi Yasak <alpernebiyasak@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
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23
doc/device-tree-bindings/pwm/cros-ec-pwm.txt
Normal file
23
doc/device-tree-bindings/pwm/cros-ec-pwm.txt
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@ -0,0 +1,23 @@
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PWM controlled by ChromeOS EC
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Google's ChromeOS EC PWM is a simple PWM attached to the Embedded Controller
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(EC) and controlled via a host-command interface.
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An EC PWM node should be only found as a sub-node of the EC node (see
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doc/device-tree-bindings/misc/cros-ec.txt).
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Required properties:
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- compatible: Must contain "google,cros-ec-pwm"
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- #pwm-cells: Should be 1. The cell specifies the PWM index.
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Example:
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cros-ec@0 {
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compatible = "google,cros-ec-spi";
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...
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cros_ec_pwm: ec-pwm {
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compatible = "google,cros-ec-pwm";
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#pwm-cells = <1>;
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};
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};
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@ -1170,6 +1170,23 @@ int cros_ec_battery_cutoff(struct udevice *dev, uint8_t flags)
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return 0;
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}
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int cros_ec_set_pwm_duty(struct udevice *dev, uint8_t index, uint16_t duty)
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{
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struct ec_params_pwm_set_duty p;
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int ret;
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p.duty = duty;
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p.pwm_type = EC_PWM_TYPE_GENERIC;
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p.index = index;
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ret = ec_command(dev, EC_CMD_PWM_SET_DUTY, 0, &p, sizeof(p),
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NULL, 0);
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if (ret < 0)
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return ret;
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return 0;
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}
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int cros_ec_set_ldo(struct udevice *dev, uint8_t index, uint8_t state)
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{
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struct ec_params_ldo_set params;
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@ -9,6 +9,15 @@ config DM_PWM
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frequency/period can be controlled along with the proportion of that
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time that the signal is high.
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config PWM_CROS_EC
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bool "Enable support for the Chrome OS EC PWM"
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depends on DM_PWM
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help
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This PWM is found on several Chrome OS devices and controlled by
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the Chrome OS embedded controller. It may be used to control the
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screen brightness and/or the keyboard backlight depending on the
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device.
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config PWM_EXYNOS
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bool "Enable support for the Exynos PWM"
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depends on DM_PWM
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@ -10,6 +10,7 @@
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obj-$(CONFIG_DM_PWM) += pwm-uclass.o
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obj-$(CONFIG_PWM_CROS_EC) += cros_ec_pwm.o
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obj-$(CONFIG_PWM_EXYNOS) += exynos_pwm.o
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obj-$(CONFIG_PWM_IMX) += pwm-imx.o pwm-imx-util.o
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obj-$(CONFIG_PWM_MESON) += pwm-meson.o
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84
drivers/pwm/cros_ec_pwm.c
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84
drivers/pwm/cros_ec_pwm.c
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// SPDX-License-Identifier: GPL-2.0+
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#include <common.h>
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#include <cros_ec.h>
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#include <dm.h>
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#include <errno.h>
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#include <log.h>
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#include <pwm.h>
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struct cros_ec_pwm_priv {
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bool enabled;
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uint duty;
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};
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static int cros_ec_pwm_set_config(struct udevice *dev, uint channel,
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uint period_ns, uint duty_ns)
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{
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struct cros_ec_pwm_priv *priv = dev_get_priv(dev);
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uint duty;
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int ret;
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debug("%s: period_ns=%u, duty_ns=%u asked\n", __func__,
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period_ns, duty_ns);
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/* No way to set the period, only a relative duty cycle */
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duty = EC_PWM_MAX_DUTY * duty_ns / period_ns;
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if (duty > EC_PWM_MAX_DUTY)
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duty = EC_PWM_MAX_DUTY;
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if (!priv->enabled) {
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priv->duty = duty;
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debug("%s: duty=%#x to-be-set\n", __func__, duty);
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return 0;
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}
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ret = cros_ec_set_pwm_duty(dev->parent, channel, duty);
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if (ret) {
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debug("%s: duty=%#x failed\n", __func__, duty);
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return ret;
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}
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priv->duty = duty;
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debug("%s: duty=%#x set\n", __func__, duty);
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return 0;
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}
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static int cros_ec_pwm_set_enable(struct udevice *dev, uint channel,
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bool enable)
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{
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struct cros_ec_pwm_priv *priv = dev_get_priv(dev);
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int ret;
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ret = cros_ec_set_pwm_duty(dev->parent, channel,
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enable ? priv->duty : 0);
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if (ret) {
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debug("%s: enable=%d failed\n", __func__, enable);
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return ret;
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}
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priv->enabled = enable;
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debug("%s: enable=%d (duty=%#x) set\n", __func__,
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enable, priv->duty);
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return 0;
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}
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static const struct pwm_ops cros_ec_pwm_ops = {
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.set_config = cros_ec_pwm_set_config,
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.set_enable = cros_ec_pwm_set_enable,
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};
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static const struct udevice_id cros_ec_pwm_ids[] = {
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{ .compatible = "google,cros-ec-pwm" },
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{ }
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};
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U_BOOT_DRIVER(cros_ec_pwm) = {
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.name = "cros_ec_pwm",
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.id = UCLASS_PWM,
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.of_match = cros_ec_pwm_ids,
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.ops = &cros_ec_pwm_ops,
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.priv_auto_alloc_size = sizeof(struct cros_ec_pwm_priv),
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};
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@ -512,6 +512,19 @@ int cros_ec_efs_verify(struct udevice *dev, enum ec_flash_region region);
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*/
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int cros_ec_battery_cutoff(struct udevice *dev, uint8_t flags);
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/**
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* cros_ec_set_pwm_duty() - Set duty cycle of a generic pwm
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*
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* Note that duty value needs to be passed to the EC as a 16 bit number
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* for increased precision.
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*
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* @param dev CROS-EC device
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* @param index Index of the pwm
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* @param duty Desired duty cycle, in 0..EC_PWM_MAX_DUTY range.
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* @return 0 if OK, -ve on error
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*/
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int cros_ec_set_pwm_duty(struct udevice *dev, uint8_t index, uint16_t duty);
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/**
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* cros_ec_read_limit_power() - Check if power is limited by batter/charger
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*
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