[PATCH v3 1/2] video: backlight: Support PWMs without a known period_ns
The PWM device provided by Chrome OS EC doesn't really support anything other than setting a relative duty cycle. To support it as a backlight, this patch makes the PWM period optional in the device tree and pretends the valid brightness range is its period_ns.
Also adds a sandbox test for a PWM channel that has a fixed period, checking that the resulting duty_cycle matches on a set_config() even if the requested period_ns can't be set.
Signed-off-by: Alper Nebi Yasak alpernebiyasak@gmail.com Reviewed-by: Simon Glass sjg@chromium.org ---
Changes in v3: - Add tag: "Reviewed-by: Simon Glass sjg@chromium.org" - Adjust to match recently merged duty cycle calculation fix.
v2: https://patchwork.ozlabs.org/project/uboot/patch/20200926200851.4388-1-alper...
Changes in v2: - Add sandbox test to pwm.c (using sandbox_pwm's channel 2) - Add comments to pwm_set_config() and pwm_ops->set_config()
v1: https://patchwork.ozlabs.org/project/uboot/patch/20200923165231.18188-1-alpe...
drivers/pwm/sandbox_pwm.c | 11 +++++++++-- drivers/video/pwm_backlight.c | 20 ++++++++++++++------ include/pwm.h | 8 ++++++++ test/dm/pwm.c | 11 +++++++++++ 4 files changed, 42 insertions(+), 8 deletions(-)
diff --git a/drivers/pwm/sandbox_pwm.c b/drivers/pwm/sandbox_pwm.c index 28988187e039..3fd2e78c909d 100644 --- a/drivers/pwm/sandbox_pwm.c +++ b/drivers/pwm/sandbox_pwm.c @@ -59,8 +59,15 @@ static int sandbox_pwm_set_config(struct udevice *dev, uint channel, if (channel >= NUM_CHANNELS) return -ENOSPC; chan = &priv->chan[channel]; - chan->period_ns = period_ns; - chan->duty_ns = duty_ns; + + if (channel == 2) { + /* Pretend to have some fixed period */ + chan->period_ns = 4096; + chan->duty_ns = duty_ns * 4096 / period_ns; + } else { + chan->period_ns = period_ns; + chan->duty_ns = duty_ns; + }
return 0; } diff --git a/drivers/video/pwm_backlight.c b/drivers/video/pwm_backlight.c index 9519180ceb39..18b7a00b033c 100644 --- a/drivers/video/pwm_backlight.c +++ b/drivers/video/pwm_backlight.c @@ -62,10 +62,17 @@ static int set_pwm(struct pwm_backlight_priv *priv) uint duty_cycle; int ret;
- duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) / - (priv->max_level - priv->min_level); - ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns, - duty_cycle); + if (priv->period_ns) { + duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) / + (priv->max_level - priv->min_level); + ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns, + duty_cycle); + } else { + /* PWM driver will internally scale these like the above. */ + ret = pwm_set_config(priv->pwm, priv->channel, + priv->max_level - priv->min_level, + priv->cur_level - priv->min_level); + } if (ret) return log_ret(ret);
@@ -213,10 +220,11 @@ static int pwm_backlight_ofdata_to_platdata(struct udevice *dev) log_debug("Cannot get PWM: ret=%d\n", ret); return log_ret(ret); } - if (args.args_count < 2) + if (args.args_count < 1) return log_msg_ret("Not enough arguments to pwm\n", -EINVAL); priv->channel = args.args[0]; - priv->period_ns = args.args[1]; + if (args.args_count > 1) + priv->period_ns = args.args[1]; if (args.args_count > 2) priv->polarity = args.args[2];
diff --git a/include/pwm.h b/include/pwm.h index 54ae3e64c310..97bda0856e6c 100644 --- a/include/pwm.h +++ b/include/pwm.h @@ -15,6 +15,10 @@ struct pwm_ops { /** * set_config() - Set the PWM configuration * + * Change both the PWM device's period and it's duty period if + * possible. Otherwise, set an appropriate duty period that best + * matches the given period_ns / duty_ns ratio for the device. + * * @dev: PWM device to update * @channel: PWM channel to update * @period_ns: PWM period in nanoseconds @@ -49,6 +53,10 @@ struct pwm_ops { /** * pwm_set_config() - Set the PWM configuration * + * Change both the PWM device's period and it's duty period if + * possible. Otherwise, set an appropriate duty period that best + * matches the given period_ns / duty_ns ratio for the device. + * * @dev: PWM device to update * @channel: PWM channel to update * @period_ns: PWM period in nanoseconds diff --git a/test/dm/pwm.c b/test/dm/pwm.c index 0de6dba1ba64..b624cf3d6558 100644 --- a/test/dm/pwm.c +++ b/test/dm/pwm.c @@ -6,6 +6,7 @@ #include <common.h> #include <dm.h> #include <pwm.h> +#include <asm/test.h> #include <dm/test.h> #include <test/test.h> #include <test/ut.h> @@ -14,6 +15,10 @@ static int dm_test_pwm_base(struct unit_test_state *uts) { struct udevice *dev; + uint period_ns; + uint duty_ns; + bool enable; + bool polarity;
ut_assertok(uclass_get_device(UCLASS_PWM, 0, &dev)); ut_assertnonnull(dev); @@ -24,6 +29,12 @@ static int dm_test_pwm_base(struct unit_test_state *uts) ut_asserteq(-ENOSPC, pwm_set_enable(dev, 3, true)); ut_assertok(pwm_set_invert(dev, 0, true));
+ ut_assertok(pwm_set_config(dev, 2, 100, 50)); + ut_assertok(sandbox_pwm_get_config(dev, 2, &period_ns, &duty_ns, + &enable, &polarity)); + ut_asserteq(period_ns, 4096); + ut_asserteq(duty_ns, 50 * 4096 / 100); + ut_assertok(uclass_get_device(UCLASS_PWM, 1, &dev)); ut_asserteq(-ENODEV, uclass_get_device(UCLASS_PWM, 2, &dev));
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 --- I'm testing on a rk3399-gru-kevin with a lot of other patches to get it and it's screen working. The actual tree I'm testing is available here:
https://github.com/alpernebbi/u-boot/tree/rk3399-gru-kevin/wip (currently at commit 1c016682bf84b82488311d59adc81691de2a664f)
Changes in v3: - Add tag: "Reviewed-by: Simon Glass sjg@chromium.org"
v2: https://patchwork.ozlabs.org/project/uboot/patch/20200926200851.4388-2-alper...
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-alpe...
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 000000000000..f198d088917b --- /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 a5534b16673b..3be2dd6f14ac 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 b3bd5c6bb7ae..ef17330387bc 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 f21ae7d76eeb..d7458e33a9a8 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_MESON) += pwm-meson.o diff --git a/drivers/pwm/cros_ec_pwm.c b/drivers/pwm/cros_ec_pwm.c new file mode 100644 index 000000000000..44f4105dfd54 --- /dev/null +++ b/drivers/pwm/cros_ec_pwm.c @@ -0,0 +1,84 @@ +// 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); + + 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 f4b9b7a5c26e..202e5c2c74a6 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 *
On Thu, 22 Oct 2020 23:49:27 +0300 Alper Nebi Yasak alpernebiyasak@gmail.com wrote: ...
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
applied to u-boot-video/master, thanks!
-- Anatolij
On Thu, 22 Oct 2020 23:49:26 +0300 Alper Nebi Yasak alpernebiyasak@gmail.com wrote: ...
drivers/pwm/sandbox_pwm.c | 11 +++++++++-- drivers/video/pwm_backlight.c | 20 ++++++++++++++------ include/pwm.h | 8 ++++++++ test/dm/pwm.c | 11 +++++++++++ 4 files changed, 42 insertions(+), 8 deletions(-)
applied to u-boot-video/master, thanks!
-- Anatolij
participants (2)
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Alper Nebi Yasak -
Anatolij Gustschin