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Subject[PATCH V5 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 fans with a tachometer
output signal, which generate a defined number of pulses per revolution.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
---
drivers/hwmon/pwm-fan.c | 107 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 103 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index e4c5197..8c4c5ee 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 +136,47 @@ 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);
+ struct device_attribute *devattr;
+
+ /* Hide fan_input in case no interrupt is available */
+ devattr = container_of(a, struct device_attribute, attr);
+ 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 +282,7 @@ 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 +302,10 @@ 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 +334,38 @@ 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 +376,7 @@ 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 +384,9 @@ 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 +403,8 @@ 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);

--
2.7.4
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