[PATCH 2/2] pwm: Add a driver for Chrome OS EC PWM
Simon Glass
sjg at chromium.org
Thu Sep 24 18:08:08 CEST 2020
Hi Alper,
On Wed, 23 Sep 2020 at 10:52, Alper Nebi Yasak <alpernebiyasak at gmail.com> wrote:
>
> 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.
>
> Signed-off-by: Alper Nebi Yasak <alpernebiyasak at gmail.com>
> ---
> 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 2cdb2cc4fb503dd5f6958e8f30406293e90b835)
>
> drivers/misc/cros_ec.c | 14 +++++++
> drivers/pwm/Kconfig | 9 +++++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/cros_ec_pwm.c | 82 +++++++++++++++++++++++++++++++++++++++
> include/cros_ec.h | 13 +++++++
> 5 files changed, 119 insertions(+)
> create mode 100644 drivers/pwm/cros_ec_pwm.c
This looks good, but please add a devicetree binding file. Is this the
same as is used in Linux?
>
> diff --git a/drivers/misc/cros_ec.c b/drivers/misc/cros_ec.c
> index a5534b1667..a9a1eb8a25 100644
> --- a/drivers/misc/cros_ec.c
> +++ b/drivers/misc/cros_ec.c
> @@ -1110,6 +1110,20 @@ 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;
> +
> + p.duty = duty;
> + p.pwm_type = EC_PWM_TYPE_GENERIC;
> + p.index = index;
> +
> + if (ec_command(dev, EC_CMD_PWM_SET_DUTY, 0, &p, sizeof(p),
> + NULL, 0) < 0)
> + return -1;
Please return the error you got. Also -1 is -EPERM which is not what
you mean here.
> + 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..781f1a1eae
> --- /dev/null
> +++ b/drivers/pwm/cros_ec_pwm.c
> @@ -0,0 +1,82 @@
> +// 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)
> + 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);
blank line before last return in function. Same below
> + 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
> *
> --
> 2.28.0
>
Regards,
Simon
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