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>

1 files changed, 101 insertions, 4 deletions

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index e4c5197417a8..285ec3abb85e 100644
--- 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);