[PATCH v3 8/8] hwmon: pwm-fan: Code for using PWM FAN as a cooling device

Lukasz Majewski
2015-02-06T17:00:40Z

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@samsung.com>
---
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
---
drivers/hwmon/pwm-fan.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 83 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index f3f5843..79fe24e 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;
@@ -113,7 +179,7 @@ int pwm_fan_of_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx)

if (ret == -EINVAL) {
dev_err(dev, "Property 'cooling-levels' not found\n");
- return 0;
+ return ret;
}

if (ret <= 0) {
@@ -149,8 +215,9 @@ 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;

@@ -194,8 +261,21 @@ static int pwm_fan_probe(struct platform_device *pdev)
}

ret = pwm_fan_of_get_cooling_data(&pdev->dev, ctx);
- if (ret)
+ if (!ret) {
+ ctx->pwm_fan_state = ctx->pwm_fan_max_state;
+ 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);
+ } else if (ret != -EINVAL) {
return ret;
+ }

return 0;
}
--
2.0.0.rc2