[PATCH v5 6/6] hwmon: pwm-fan: Code for using PWM FAN as a cooling device

[Lukasz Majewski <l.majewski@xxxxxxxxxxx>]

The PWM FAN device can now be used as a thermal cooling device. Necessary
infrastructure has been added in this commit.

Signed-off-by: Lukasz Majewski <l.majewski@xxxxxxxxxxx>
---
Changes for v2:
- Replace pwm_fan_cooling_states with pwm_fan_cooling_levels
- Update ctx->pwm_fan_state when correct data from device tree is available
- Using therma_cdev_update() when thermal is ready for controlling the fan
Changes for v3:
- Rename patch heading
- pwm_fan_of_get_cooling_data() now returns -EINVAL when no "cooling-levels"
  property defined
- register of cooling device only when proper cooling data is present
Changes for v4:
- None
Changes for v5:
- Check for IS_ENABLED(CONFIG_THERMAL) has been added to prevent from
  executing thermal_* specific functions
---
 drivers/hwmon/pwm-fan.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 82 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index e6ed353..2c1a8f0 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -24,6 +24,7 @@
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 #include <linux/sysfs.h>
+#include <linux/thermal.h>
 
 #define MAX_PWM 255
 
@@ -68,6 +69,17 @@ exit_set_pwm_err:
 	return ret;
 }
 
+static void pwm_fan_update_state(struct pwm_fan_ctx *ctx, unsigned long pwm)
+{
+	int i;
+
+	for (i = 0; i < ctx->pwm_fan_max_state; ++i)
+		if (pwm < ctx->pwm_fan_cooling_levels[i + 1])
+			break;
+
+	ctx->pwm_fan_state = i;
+}
+
 static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 		       const char *buf, size_t count)
 {
@@ -82,6 +94,7 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 	if (ret)
 		return ret;
 
+	pwm_fan_update_state(ctx, pwm);
 	return count;
 }
 
@@ -103,6 +116,59 @@ static struct attribute *pwm_fan_attrs[] = {
 
 ATTRIBUTE_GROUPS(pwm_fan);
 
+/* thermal cooling device callbacks */
+static int pwm_fan_get_max_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct pwm_fan_ctx *ctx = cdev->devdata;
+
+	*state = ctx->pwm_fan_max_state;
+
+	return 0;
+}
+
+static int pwm_fan_get_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct pwm_fan_ctx *ctx = cdev->devdata;
+
+	if (!ctx)
+		return -EINVAL;
+
+	*state = ctx->pwm_fan_state;
+
+	return 0;
+}
+
+static int
+pwm_fan_set_cur_state(struct thermal_cooling_device *cdev, unsigned long state)
+{
+	struct pwm_fan_ctx *ctx = cdev->devdata;
+	int ret;
+
+	if (!ctx || (state > ctx->pwm_fan_max_state))
+		return -EINVAL;
+
+	if (state == ctx->pwm_fan_state)
+		return 0;
+
+	ret = __set_pwm(ctx, ctx->pwm_fan_cooling_levels[state]);
+	if (ret) {
+		dev_err(&cdev->device, "Cannot set pwm!\n");
+		return ret;
+	}
+
+	ctx->pwm_fan_state = state;
+
+	return ret;
+}
+
+static const struct thermal_cooling_device_ops pwm_fan_cooling_ops = {
+	.get_max_state = pwm_fan_get_max_state,
+	.get_cur_state = pwm_fan_get_cur_state,
+	.set_cur_state = pwm_fan_set_cur_state,
+};
+
 int pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx)
 {
 	struct device_node *np = dev->of_node;
@@ -145,8 +211,9 @@ int pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx)
 
 static int pwm_fan_probe(struct platform_device *pdev)
 {
-	struct device *hwmon;
+	struct thermal_cooling_device *cdev;
 	struct pwm_fan_ctx *ctx;
+	struct device *hwmon;
 	int duty_cycle;
 	int ret;
 
@@ -193,6 +260,20 @@ static int pwm_fan_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ctx->pwm_fan_state = ctx->pwm_fan_max_state;
+	if (IS_ENABLED(CONFIG_THERMAL)) {
+		cdev = thermal_of_cooling_device_register(pdev->dev.of_node,
+							  "pwm-fan", ctx,
+							  &pwm_fan_cooling_ops);
+		if (IS_ERR(cdev)) {
+			dev_err(&pdev->dev,
+				"Failed to register pwm-fan as cooling device");
+			pwm_disable(ctx->pwm);
+			return PTR_ERR(cdev);
+		}
+		thermal_cdev_update(cdev);
+	}
+
 	return 0;
 }
 
-- 
2.0.0.rc2

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