linux-kernel - [PATCH v2 2/4] hwmon: (cros_ec) Add support for fan target speed

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Message-Id: <20260118-cros_ec-hwmon-pwm-v2-2-77eb1709b031@weissschuh.net>
Date: Sun, 18 Jan 2026 10:45:56 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Benson Leung <bleung@...omium.org>, Tzung-Bi Shih <tzungbi@...nel.org>, 
 Guenter Roeck <groeck@...omium.org>, 
 Thomas Weißschuh <thomas@...ssschuh.net>, 
 Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>, 
 Jonathan Corbet <corbet@....net>
Cc: Dustin Howett <dustin@...ett.net>, 
 Mario Limonciello <mario.limonciello@....com>, 
 Stephen Horvath <s.horvath@...look.com.au>, chrome-platform@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org, 
 Sung-Chi Li <lschyi@...omium.org>, linux-doc@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v2 2/4] hwmon: (cros_ec) Add support for fan target speed

Use EC_CMD_PWM_GET_FAN_TARGET_RPM to retrieve the target fan speed.
The EC only supports this for the first fan.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 Documentation/hwmon/cros_ec_hwmon.rst |  3 +++
 drivers/hwmon/cros_ec_hwmon.c         | 26 +++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/Documentation/hwmon/cros_ec_hwmon.rst b/Documentation/hwmon/cros_ec_hwmon.rst
index b7dc88d22fda..ebc8da48fa8a 100644
--- a/Documentation/hwmon/cros_ec_hwmon.rst
+++ b/Documentation/hwmon/cros_ec_hwmon.rst
@@ -29,6 +29,9 @@ Supported features
 Fan readings
     Always supported.
 
+Fan target speed
+    If supported by the EC.
+
 Temperature readings
     Always supported.
 
diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
index 48331703f2f5..53abd55cba05 100644
--- a/drivers/hwmon/cros_ec_hwmon.c
+++ b/drivers/hwmon/cros_ec_hwmon.c
@@ -86,6 +86,20 @@ static int cros_ec_hwmon_read_pwm_enable(struct cros_ec_device *cros_ec, u8 inde
 	return 0;
 }
 
+static int cros_ec_hwmon_read_fan_target(struct cros_ec_device *cros_ec, u16 *speed)
+{
+	struct ec_response_pwm_get_fan_rpm resp;
+	int ret;
+
+	ret = cros_ec_cmd(cros_ec, 0, EC_CMD_PWM_GET_FAN_TARGET_RPM,
+			  NULL, 0, &resp, sizeof(resp));
+	if (ret < 0)
+		return ret;
+
+	*speed = resp.rpm;
+	return 0;
+}
+
 static int cros_ec_hwmon_read_temp(struct cros_ec_device *cros_ec, u8 index, u8 *temp)
 {
 	unsigned int offset;
@@ -143,6 +157,11 @@ static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 			ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
 			if (ret == 0)
 				*val = cros_ec_hwmon_is_error_fan(speed);
+
+		} else if (attr == hwmon_fan_target) {
+			ret = cros_ec_hwmon_read_fan_target(priv->cros_ec, &speed);
+			if (ret == 0)
+				*val = speed;
 		}
 	} else if (type == hwmon_pwm) {
 		if (attr == hwmon_pwm_enable) {
@@ -259,8 +278,13 @@ static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_type
 					u32 attr, int channel)
 {
 	const struct cros_ec_hwmon_priv *priv = data;
+	u16 speed;
 
 	if (type == hwmon_fan) {
+		if (attr == hwmon_fan_target &&
+		    cros_ec_hwmon_read_fan_target(priv->cros_ec, &speed) == -EOPNOTSUPP)
+			return 0;
+
 		if (priv->usable_fans & BIT(channel))
 			return 0444;
 	} else if (type == hwmon_pwm) {
@@ -277,7 +301,7 @@ static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_type
 static const struct hwmon_channel_info * const cros_ec_hwmon_info[] = {
 	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
 	HWMON_CHANNEL_INFO(fan,
-			   HWMON_F_INPUT | HWMON_F_FAULT,
+			   HWMON_F_INPUT | HWMON_F_FAULT | HWMON_F_TARGET,
 			   HWMON_F_INPUT | HWMON_F_FAULT,
 			   HWMON_F_INPUT | HWMON_F_FAULT,
 			   HWMON_F_INPUT | HWMON_F_FAULT),

-- 
2.52.0