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Subject[PATCH RFC 3/3] hwmon: pwm-fan: Add RPM support via external interrupt
Date
This adds RPM support to the pwm-fan driver in order to use with
fancontrol/pwmconfig. This feature is intended for 2 pulse-per-revolution
fans which provides a tachometer output signal.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
---
drivers/hwmon/pwm-fan.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 9e0591e..731fdc6 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>
@@ -26,13 +27,22 @@
#include <linux/regulator/consumer.h>
#include <linux/sysfs.h>
#include <linux/thermal.h>
+#include <linux/timer.h>

#define MAX_PWM 255
+#define SAMPLE_TIME 1 /* seconds */
+#define PULSE_PER_REVOLUTION 2

struct pwm_fan_ctx {
struct mutex lock;
struct pwm_device *pwm;
struct regulator *reg_en;
+
+ int irq;
+ unsigned int pulses;
+ unsigned int rpm;
+ struct timer_list sample_timer;
+
unsigned int pwm_value;
unsigned int pwm_fan_state;
unsigned int pwm_fan_max_state;
@@ -40,6 +50,27 @@ struct pwm_fan_ctx {
struct thermal_cooling_device *cdev;
};

+static irqreturn_t pulse_handler(int irq, void *dev_id)
+{
+ struct pwm_fan_ctx *ctx = dev_id;
+
+ if (ctx->pulses < INT_MAX / 2)
+ ctx->pulses++;
+
+ return IRQ_HANDLED;
+}
+
+static void sample_timer(struct timer_list *t)
+{
+ struct pwm_fan_ctx *ctx = from_timer(ctx, t, sample_timer);
+ unsigned int pulses;
+
+ pulses = ctx->pulses;
+ ctx->pulses -= pulses;
+ ctx->rpm = pulses * 60 / SAMPLE_TIME / PULSE_PER_REVOLUTION;
+ mod_timer(&ctx->sample_timer, jiffies + (HZ * SAMPLE_TIME));
+}
+
static int __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
{
unsigned long period;
@@ -100,11 +131,20 @@ 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,
};

@@ -263,6 +303,19 @@ static int pwm_fan_probe(struct platform_device *pdev)
}
}

+ timer_setup(&ctx->sample_timer, sample_timer, 0);
+
+ ctx->irq = platform_get_irq(pdev, 0);
+ 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");
+ return ret;
+ }
+ mod_timer(&ctx->sample_timer, jiffies + (HZ * SAMPLE_TIME));
+ }
+
hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, "pwmfan",
ctx, pwm_fan_groups);
if (IS_ERR(hwmon)) {
@@ -304,6 +357,8 @@ 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->sample_timer);
+
if (ctx->pwm_value)
pwm_disable(ctx->pwm);

--
2.7.4
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