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Message-ID: <a89ee43f-79d9-405a-a099-7ce90fe6eb55@t-8ch.de>
Date: Sat, 3 May 2025 09:36:39 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: lschyi@...omium.org
Cc: Benson Leung <bleung@...omium.org>,
Guenter Roeck <groeck@...omium.org>, Jean Delvare <jdelvare@...e.com>,
Guenter Roeck <linux@...ck-us.net>, Jonathan Corbet <corbet@....net>,
chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
linux-doc@...r.kernel.org, Sung-Chi Li <lschyi@...gle.com>
Subject: Re: [PATCH v2 2/3] hwmon: (cros_ec) add PWM control over fans
On 2025-05-02 13:34:46+0800, Sung-Chi Li via B4 Relay wrote:
> From: Sung-Chi Li <lschyi@...omium.org>
>
> Newer EC firmware supports controlling fans through host commands, so
> adding corresponding implementations for controlling these fans in the
> driver for other kernel services and userspace to control them.
>
> The driver will first probe the supported host command versions (get and
> set of fan PWM values, get and set of fan control mode) to see if the
> connected EC fulfills the requirements of controlling the fan, then
> exposes corresponding sysfs nodes for userspace to control the fan with
> corresponding read and write implementations.
> As EC will automatically change the fan mode to auto when the device is
> suspended, the power management hooks are added as well to keep the fan
> control mode and fan PWM value consistent during suspend and resume. As
> we need to access the hwmon device in the power management hook, update
> the driver by storing the hwmon device in the driver data as well.
>
> Signed-off-by: Sung-Chi Li <lschyi@...omium.org>
> ---
> Documentation/hwmon/cros_ec_hwmon.rst | 5 +-
> drivers/hwmon/cros_ec_hwmon.c | 201 ++++++++++++++++++++++++++++++++++
> 2 files changed, 205 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/hwmon/cros_ec_hwmon.rst b/Documentation/hwmon/cros_ec_hwmon.rst
> index 47ecae983bdbef4bfcafc5dd2fff3de039f77f8e..5b802be120438732529c3d25b1afa8b4ee353305 100644
> --- a/Documentation/hwmon/cros_ec_hwmon.rst
> +++ b/Documentation/hwmon/cros_ec_hwmon.rst
> @@ -23,4 +23,7 @@ ChromeOS embedded controller used in Chromebooks and other devices.
>
> The channel labels exposed via hwmon are retrieved from the EC itself.
>
> -Fan and temperature readings are supported.
> +Fan and temperature readings are supported. PWM fan control is also supported if
> +the EC also supports setting fan PWM values and fan mode. Note that EC will
> +switch fan control mode back to auto when suspended. This driver will restore
> +the fan state before suspended.
> diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
> index 9991c3fa020ac859cbbff29dfb669e53248df885..c5e42e2a03a0c8c68d3f8afbb2bb45b93a58b955 100644
> --- a/drivers/hwmon/cros_ec_hwmon.c
> +++ b/drivers/hwmon/cros_ec_hwmon.c
> @@ -7,6 +7,7 @@
>
> #include <linux/device.h>
> #include <linux/hwmon.h>
> +#include <linux/math.h>
> #include <linux/mod_devicetable.h>
> #include <linux/module.h>
> #include <linux/platform_device.h>
> @@ -21,6 +22,9 @@ struct cros_ec_hwmon_priv {
> struct cros_ec_device *cros_ec;
> const char *temp_sensor_names[EC_TEMP_SENSOR_ENTRIES + EC_TEMP_SENSOR_B_ENTRIES];
> u8 usable_fans;
> + bool fan_control_supported;
> + u8 manual_fans; /* bits to indicate whether the fan is set to manual */
> + u8 manual_fan_pwm_values[EC_FAN_SPEED_ENTRIES];
> };
>
> static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index, u16 *speed)
> @@ -36,6 +40,40 @@ static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index
> return 0;
> }
>
> +static int cros_ec_hwmon_read_pwm_value(struct cros_ec_device *cros_ec, u8 index, u8 *pwm_value)
> +{
> + struct ec_params_pwm_get_fan_duty req = {
> + .fan_idx = index,
> + };
> + struct ec_response_pwm_get_fan_duty resp;
> + int ret = cros_ec_cmd(cros_ec, 0, EC_CMD_PWM_GET_FAN_DUTY, &req, sizeof(req),
> + &resp, sizeof(resp));
As mentioned before, please split the variable declaration and the
assignment.
> +
> + if (ret < 0)
> + return ret;
> +
> + *pwm_value = (u8)DIV_ROUND_CLOSEST(le32_to_cpu(resp.percent) * 255, 100);
> + return 0;
> +}
> +
> +static int cros_ec_hwmon_read_pwm_enable(struct cros_ec_device *cros_ec, u8 index,
> + u8 *control_method)
> +{
> + struct ec_params_auto_fan_ctrl_v2 req = {
> + .cmd = EC_AUTO_FAN_CONTROL_CMD_GET,
> + .fan_idx = index,
> + };
> + struct ec_response_auto_fan_control resp;
> + int ret = cros_ec_cmd(cros_ec, 2, EC_CMD_THERMAL_AUTO_FAN_CTRL, &req, sizeof(req),
> + &resp, sizeof(resp));
> +
> + if (ret < 0)
> + return ret;
> +
> + *control_method = resp.is_auto ? 2 : 1;
> + return 0;
> +}
> +
> static int cros_ec_hwmon_read_temp(struct cros_ec_device *cros_ec, u8 index, u8 *temp)
> {
> unsigned int offset;
> @@ -76,6 +114,8 @@ static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
> int ret = -EOPNOTSUPP;
> u16 speed;
> + u8 control_method;
> + u8 pwm_value;
Ordering.
> u8 temp;
>
> if (type == hwmon_fan) {
> @@ -92,6 +132,17 @@ static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> if (ret == 0)
> *val = cros_ec_hwmon_is_error_fan(speed);
> }
> + } else if (type == hwmon_pwm) {
> + if (attr == hwmon_pwm_enable) {
> + ret = cros_ec_hwmon_read_pwm_enable(priv->cros_ec, channel,
> + &control_method);
Unnecessary linbreak.
> + if (ret == 0)
> + *val = control_method;
> + } else if (attr == hwmon_pwm_input) {
> + ret = cros_ec_hwmon_read_pwm_value(priv->cros_ec, channel, &pwm_value);
> + if (ret == 0)
> + *val = pwm_value;
> + }
> } else if (type == hwmon_temp) {
> if (attr == hwmon_temp_input) {
> ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
> @@ -124,6 +175,72 @@ static int cros_ec_hwmon_read_string(struct device *dev, enum hwmon_sensor_types
> return -EOPNOTSUPP;
> }
>
> +static int cros_ec_hwmon_set_fan_pwm_val(struct cros_ec_device *cros_ec, u8 index, u8 val)
> +{
> + int ret;
> + struct ec_params_pwm_set_fan_duty_v1 req = {
> + .fan_idx = index,
> + .percent = DIV_ROUND_CLOSEST((uint32_t)val * 100, 255),
> + };
> +
> + ret = cros_ec_cmd(cros_ec, 1, EC_CMD_PWM_SET_FAN_DUTY, &req, sizeof(req), NULL, 0);
> + if (ret < 0)
> + return ret;
> + return 0;
> +}
> +
> +static int cros_ec_hwmon_write_pwm_input(struct cros_ec_device *cros_ec, u8 index, u8 val)
> +{
> + u8 control_method;
> + int ret;
> +
> + ret = cros_ec_hwmon_read_pwm_enable(cros_ec, index, &control_method);
> + if (ret)
> + return ret;
> + if (control_method != 1)
> + return -EOPNOTSUPP;
> +
> + return cros_ec_hwmon_set_fan_pwm_val(cros_ec, index, val);
> +}
> +
> +static int cros_ec_hwmon_write_pwm_enable(struct cros_ec_device *cros_ec, u8 index, u8 val)
> +{
> + int ret;
> + struct ec_params_auto_fan_ctrl_v2 req = {
> + .fan_idx = index,
> + .cmd = EC_AUTO_FAN_CONTROL_CMD_SET,
> + };
> +
> + /* No CROS EC supports no fan speed control */
> + if (val == 0)
> + return -EOPNOTSUPP;
> +
> + req.set_auto = (val != 1) ? true : false;
> + ret = cros_ec_cmd(cros_ec, 2, EC_CMD_THERMAL_AUTO_FAN_CTRL, &req, sizeof(req), NULL, 0);
> + if (ret < 0)
> + return ret;
> + return 0;
> +}
> +
> +static int cros_ec_hwmon_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> + int channel, long val)
> +{
> + struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
> +
> + if (type == hwmon_pwm) {
> + switch (attr) {
> + case hwmon_pwm_input:
> + return cros_ec_hwmon_write_pwm_input(priv->cros_ec, channel, val);
> + case hwmon_pwm_enable:
> + return cros_ec_hwmon_write_pwm_enable(priv->cros_ec, channel, val);
> + default:
> + return -EOPNOTSUPP;
> + }
> + }
> +
> + return -EOPNOTSUPP;
> +}
> +
> static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_types type,
> u32 attr, int channel)
> {
> @@ -132,6 +249,9 @@ static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_type
> if (type == hwmon_fan) {
> if (priv->usable_fans & BIT(channel))
> return 0444;
> + } else if (type == hwmon_pwm) {
> + if (priv->fan_control_supported && priv->usable_fans & BIT(channel))
> + return 0644;
> } else if (type == hwmon_temp) {
> if (priv->temp_sensor_names[channel])
> return 0444;
> @@ -147,6 +267,11 @@ static const struct hwmon_channel_info * const cros_ec_hwmon_info[] = {
> HWMON_F_INPUT | HWMON_F_FAULT,
> HWMON_F_INPUT | HWMON_F_FAULT,
> HWMON_F_INPUT | HWMON_F_FAULT),
> + HWMON_CHANNEL_INFO(pwm,
> + HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> + HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> + HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
> + HWMON_PWM_INPUT | HWMON_PWM_ENABLE),
> HWMON_CHANNEL_INFO(temp,
> HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
> HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
> @@ -178,6 +303,7 @@ static const struct hwmon_channel_info * const cros_ec_hwmon_info[] = {
> static const struct hwmon_ops cros_ec_hwmon_ops = {
> .read = cros_ec_hwmon_read,
> .read_string = cros_ec_hwmon_read_string,
> + .write = cros_ec_hwmon_write,
> .is_visible = cros_ec_hwmon_is_visible,
> };
>
> @@ -233,6 +359,21 @@ static void cros_ec_hwmon_probe_fans(struct cros_ec_hwmon_priv *priv)
> }
> }
>
> +static inline bool is_cros_ec_cmd_fulfilled(struct cros_ec_device *cros_ec,
> + u16 cmd, u8 version)
> +{
> + int ret = cros_ec_get_cmd_versions(cros_ec, cmd);
> +
> + return ret >= 0 && (ret & EC_VER_MASK(version));
> +}
> +
> +static bool cros_ec_hwmon_probe_fan_control_supported(struct cros_ec_device *cros_ec)
> +{
> + return is_cros_ec_cmd_fulfilled(cros_ec, EC_CMD_PWM_GET_FAN_DUTY, 0) &&
As mentioned before, the hardcoded version constants are used in
multiple places. They should use a #define instead.
> + is_cros_ec_cmd_fulfilled(cros_ec, EC_CMD_PWM_SET_FAN_DUTY, 1) &&
> + is_cros_ec_cmd_fulfilled(cros_ec, EC_CMD_THERMAL_AUTO_FAN_CTRL, 2);
> +}
> +
> static int cros_ec_hwmon_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> @@ -259,13 +400,71 @@ static int cros_ec_hwmon_probe(struct platform_device *pdev)
>
> cros_ec_hwmon_probe_temp_sensors(dev, priv, thermal_version);
> cros_ec_hwmon_probe_fans(priv);
> + priv->fan_control_supported =
> + cros_ec_hwmon_probe_fan_control_supported(priv->cros_ec);
No need for a linebreak.
>
> hwmon_dev = devm_hwmon_device_register_with_info(dev, "cros_ec", priv,
> &cros_ec_hwmon_chip_info, NULL);
> + platform_set_drvdata(pdev, priv);
>
> return PTR_ERR_OR_ZERO(hwmon_dev);
> }
>
> +static int cros_ec_hwmon_suspend(struct platform_device *pdev, pm_message_t state)
> +{
> + struct cros_ec_hwmon_priv *priv = platform_get_drvdata(pdev);
> + size_t i;
> + int ret;
> + u8 control_method;
> +
> + if (!priv->fan_control_supported)
> + return 0;
> +
> + /* EC sets fan control to auto after suspended, store settings before suspending. */
> + for (i = 0; i < EC_FAN_SPEED_ENTRIES; i++) {
> + if (!(priv->usable_fans & BIT(i)))
> + continue;
> +
> + ret = cros_ec_hwmon_read_pwm_enable(priv->cros_ec, i, &control_method);
> + if (ret)
> + continue;
> +
> + if (control_method != 1) {
> + priv->manual_fans &= ~BIT(i);
> + continue;
> + } else {
> + priv->manual_fans |= BIT(i);
> + }
> +
> + cros_ec_hwmon_read_pwm_value(priv->cros_ec, i, &priv->manual_fan_pwm_values[i]);
> + }
> +
> + return 0;
> +}
> +
> +static int cros_ec_hwmon_resume(struct platform_device *pdev)
> +{
> + const struct cros_ec_hwmon_priv *priv = platform_get_drvdata(pdev);
> + size_t i;
> +
> + if (!priv->fan_control_supported)
> + return 0;
> +
> + /* EC sets fan control to auto after suspended, restore to settings before suspended. */
> + for (i = 0; i < EC_FAN_SPEED_ENTRIES; i++) {
> + if (!(priv->manual_fans & BIT(i)))
> + continue;
> +
> + /*
> + * Setting fan PWM value to EC will change the mode to manual for that fan in EC as
> + * well, so we do not need to issue a separate fan mode to manual call.
> + */
> + cros_ec_hwmon_set_fan_pwm_val(priv->cros_ec, i, priv->manual_fan_pwm_values[i]);
Error handling?
> + }
> +
> + return 0;
> +}
> +
> static const struct platform_device_id cros_ec_hwmon_id[] = {
> { DRV_NAME, 0 },
> {}
> @@ -274,6 +473,8 @@ static const struct platform_device_id cros_ec_hwmon_id[] = {
> static struct platform_driver cros_ec_hwmon_driver = {
> .driver.name = DRV_NAME,
> .probe = cros_ec_hwmon_probe,
> + .suspend = cros_ec_hwmon_suspend,
> + .resume = cros_ec_hwmon_resume,
I think these should use pm_ptr() to so the functions can be optimized
away if !CONFIG_PM.
> .id_table = cros_ec_hwmon_id,
> };
> module_platform_driver(cros_ec_hwmon_driver);
>
> --
> 2.49.0.906.g1f30a19c02-goog
>
>
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