[PATCH 2/2] pwm: Add a driver for Chrome OS EC PWM
Alper Nebi Yasak
alpernebiyasak at gmail.com
Fri Sep 25 18:11:49 CEST 2020
On 24/09/2020 19:08, Simon Glass wrote:
> 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?
The binding is the same as in Linux. The binding documentation file
there has been migrated to yaml, but a txt version was available as
well. I'll adapt the txt as there doesn't seem to be any yaml files in
U-Boot doc/device-tree-bindings/**.
>>
>> 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.
OK. I didn't mean -EPERM indeed, but there are still a number of other
functions in the file that do it similar to this, as far as I can tell.
>> + 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
OK.
>> + 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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