hwmon: (pwm-fan) Add RPM support via external interrupt

This adds RPM support to the pwm-fan driver in order to use with
fancontrol/pwmconfig. This feature is intended for fans with a tachometer
output signal, which generate a defined number of pulses per revolution.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
[groeck: Drop unused 'devattr' variable]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index e4c5197417a87d7c798eb6af7169b40824708378..285ec3abb85e3d34247426cdbef04e82e5bcfe54 100644 (file)
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -18,6 +18,7 @@
 
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
+#include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
@@ -26,6 +27,7 @@
 #include <linux/regulator/consumer.h>
 #include <linux/sysfs.h>
 #include <linux/thermal.h>
+#include <linux/timer.h>
 
 #define MAX_PWM 255
 
@@ -33,6 +35,14 @@ struct pwm_fan_ctx {
        struct mutex lock;
        struct pwm_device *pwm;
        struct regulator *reg_en;
+
+       int irq;
+       atomic_t pulses;
+       unsigned int rpm;
+       u8 pulses_per_revolution;
+       ktime_t sample_start;
+       struct timer_list rpm_timer;
+
        unsigned int pwm_value;
        unsigned int pwm_fan_state;
        unsigned int pwm_fan_max_state;
@@ -40,6 +50,32 @@ struct pwm_fan_ctx {
        struct thermal_cooling_device *cdev;
 };
 
+/* This handler assumes self resetting edge triggered interrupt. */
+static irqreturn_t pulse_handler(int irq, void *dev_id)
+{
+       struct pwm_fan_ctx *ctx = dev_id;
+
+       atomic_inc(&ctx->pulses);
+
+       return IRQ_HANDLED;
+}
+
+static void sample_timer(struct timer_list *t)
+{
+       struct pwm_fan_ctx *ctx = from_timer(ctx, t, rpm_timer);
+       int pulses;
+       u64 tmp;
+
+       pulses = atomic_read(&ctx->pulses);
+       atomic_sub(pulses, &ctx->pulses);
+       tmp = (u64)pulses * ktime_ms_delta(ktime_get(), ctx->sample_start) * 60;
+       do_div(tmp, ctx->pulses_per_revolution * 1000);
+       ctx->rpm = tmp;
+
+       ctx->sample_start = ktime_get();
+       mod_timer(&ctx->rpm_timer, jiffies + HZ);
+}
+
 static int  __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
 {
        unsigned long period;
@@ -100,15 +136,45 @@ static ssize_t pwm_show(struct device *dev, struct device_attribute *attr,
        return sprintf(buf, "%u\n", ctx->pwm_value);
 }
 
+static ssize_t rpm_show(struct device *dev,
+                       struct device_attribute *attr, char *buf)
+{
+       struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
+
+       return sprintf(buf, "%u\n", ctx->rpm);
+}
 
 static SENSOR_DEVICE_ATTR_RW(pwm1, pwm, 0);
+static SENSOR_DEVICE_ATTR_RO(fan1_input, rpm, 0);
 
 static struct attribute *pwm_fan_attrs[] = {
        &sensor_dev_attr_pwm1.dev_attr.attr,
+       &sensor_dev_attr_fan1_input.dev_attr.attr,
        NULL,
 };
 
-ATTRIBUTE_GROUPS(pwm_fan);
+static umode_t pwm_fan_attrs_visible(struct kobject *kobj, struct attribute *a,
+                                    int n)
+{
+       struct device *dev = container_of(kobj, struct device, kobj);
+       struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
+
+       /* Hide fan_input in case no interrupt is available  */
+       if (n == 1 && ctx->irq <= 0)
+               return 0;
+
+       return a->mode;
+}
+
+static const struct attribute_group pwm_fan_group = {
+       .attrs = pwm_fan_attrs,
+       .is_visible = pwm_fan_attrs_visible,
+};
+
+static const struct attribute_group *pwm_fan_groups[] = {
+       &pwm_fan_group,
+       NULL,
+};
 
 /* thermal cooling device callbacks */
 static int pwm_fan_get_max_state(struct thermal_cooling_device *cdev,
@@ -214,6 +280,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
        struct device *hwmon;
        int ret;
        struct pwm_state state = { };
+       u32 ppr = 2;
 
        ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
        if (!ctx)
@@ -233,6 +300,10 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
        platform_set_drvdata(pdev, ctx);
 
+       ctx->irq = platform_get_irq(pdev, 0);
+       if (ctx->irq == -EPROBE_DEFER)
+               return ctx->irq;
+
        ctx->reg_en = devm_regulator_get_optional(&pdev->dev, "fan");
        if (IS_ERR(ctx->reg_en)) {
                if (PTR_ERR(ctx->reg_en) != -ENODEV)
@@ -261,17 +332,38 @@ static int pwm_fan_probe(struct platform_device *pdev)
                goto err_reg_disable;
        }
 
+       timer_setup(&ctx->rpm_timer, sample_timer, 0);
+
+       of_property_read_u32(pdev->dev.of_node, "pulses-per-revolution", &ppr);
+       ctx->pulses_per_revolution = ppr;
+       if (!ctx->pulses_per_revolution) {
+               dev_err(&pdev->dev, "pulses-per-revolution can't be zero.\n");
+               ret = -EINVAL;
+               goto err_pwm_disable;
+       }
+
+       if (ctx->irq > 0) {
+               ret = devm_request_irq(&pdev->dev, ctx->irq, pulse_handler, 0,
+                                      pdev->name, ctx);
+               if (ret) {
+                       dev_err(&pdev->dev, "Can't get interrupt working.\n");
+                       goto err_pwm_disable;
+               }
+               ctx->sample_start = ktime_get();
+               mod_timer(&ctx->rpm_timer, jiffies + HZ);
+       }
+
        hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, "pwmfan",
                                                       ctx, pwm_fan_groups);
        if (IS_ERR(hwmon)) {
                dev_err(&pdev->dev, "Failed to register hwmon device\n");
                ret = PTR_ERR(hwmon);
-               goto err_pwm_disable;
+               goto err_del_timer;
        }
 
        ret = pwm_fan_of_get_cooling_data(&pdev->dev, ctx);
        if (ret)
-               goto err_pwm_disable;
+               goto err_del_timer;
 
        ctx->pwm_fan_state = ctx->pwm_fan_max_state;
        if (IS_ENABLED(CONFIG_THERMAL)) {
@@ -282,7 +374,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
                        dev_err(&pdev->dev,
                                "Failed to register pwm-fan as cooling device");
                        ret = PTR_ERR(cdev);
-                       goto err_pwm_disable;
+                       goto err_del_timer;
                }
                ctx->cdev = cdev;
                thermal_cdev_update(cdev);
@@ -290,6 +382,9 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
        return 0;
 
+err_del_timer:
+       del_timer_sync(&ctx->rpm_timer);
+
 err_pwm_disable:
        state.enabled = false;
        pwm_apply_state(ctx->pwm, &state);
@@ -306,6 +401,8 @@ static int pwm_fan_remove(struct platform_device *pdev)
        struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
 
        thermal_cooling_device_unregister(ctx->cdev);
+       del_timer_sync(&ctx->rpm_timer);
+
        if (ctx->pwm_value)
                pwm_disable(ctx->pwm);