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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 Reviewed-by: Simon Glass --- I'm testing on a rk3399-gru-kevin with a lot of other patches to get it (and it's screen) barely working, but using something like the following in a rk_board_late_init() added to gru.c gets the backlight to change: struct *udevice panel; uclass_first_device_err(UCLASS_PANEL, &panel); panel_enable_backlight(panel); panel_set_backlight(panel, 50); panel_set_backlight(panel, 100); The actual tree I'm testing and how I'm getting it to chainload from the vendor firmware (see commit message there) is available here: https://github.com/alpernebbi/u-boot/tree/rk3399-gru-kevin/wip (currently at commit 4b5a8441303facb6e419da9f5e86980de3eb090a) Changes in v2: - Add device-tree-binding/pwm/cros-ec-pwm.txt adapted from Linux - Return ec_command() errors correctly in cros_ec_set_pwm_duty() - Add newlines before last returns in cros_ec_pwm.c v1: https://patchwork.ozlabs.org/project/uboot/patch/20200923165231.18188-2-alpernebiyasak@gmail.com/ doc/device-tree-bindings/pwm/cros-ec-pwm.txt | 23 ++++++ drivers/misc/cros_ec.c | 17 ++++ drivers/pwm/Kconfig | 9 +++ drivers/pwm/Makefile | 1 + drivers/pwm/cros_ec_pwm.c | 84 ++++++++++++++++++++ include/cros_ec.h | 13 +++ 6 files changed, 147 insertions(+) create mode 100644 doc/device-tree-bindings/pwm/cros-ec-pwm.txt create mode 100644 drivers/pwm/cros_ec_pwm.c diff --git a/doc/device-tree-bindings/pwm/cros-ec-pwm.txt b/doc/device-tree-bindings/pwm/cros-ec-pwm.txt new file mode 100644 index 0000000000..f198d08891 --- /dev/null +++ b/doc/device-tree-bindings/pwm/cros-ec-pwm.txt @@ -0,0 +1,23 @@ +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 +doc/device-tree-bindings/misc/cros-ec.txt). + +Required properties: +- compatible: Must contain "google,cros-ec-pwm" +- #pwm-cells: Should be 1. The cell specifies the PWM index. + +Example: + cros-ec@0 { + compatible = "google,cros-ec-spi"; + + ... + + cros_ec_pwm: ec-pwm { + compatible = "google,cros-ec-pwm"; + #pwm-cells = <1>; + }; + }; diff --git a/drivers/misc/cros_ec.c b/drivers/misc/cros_ec.c index a5534b1667..3be2dd6f14 100644 --- a/drivers/misc/cros_ec.c +++ b/drivers/misc/cros_ec.c @@ -1110,6 +1110,23 @@ 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; diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 61eb468cde..73b0e5ed1e 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -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 + 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 diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index 0f4e84b04d..7af13538de 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -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_MTK) += pwm-mtk.o diff --git a/drivers/pwm/cros_ec_pwm.c b/drivers/pwm/cros_ec_pwm.c new file mode 100644 index 0000000000..44f4105dfd --- /dev/null +++ b/drivers/pwm/cros_ec_pwm.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0+ + +#include +#include +#include +#include +#include +#include + +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) + 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", + .id = UCLASS_PWM, + .of_match = cros_ec_pwm_ids, + .ops = &cros_ec_pwm_ops, + .priv_auto_alloc_size = sizeof(struct cros_ec_pwm_priv), +}; diff --git a/include/cros_ec.h b/include/cros_ec.h index f4b9b7a5c2..202e5c2c74 100644 --- a/include/cros_ec.h +++ b/include/cros_ec.h @@ -443,6 +443,19 @@ 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 *