Contrary to the gpio-fan the pwm-fan driver isn't easy to setup
with pwmconfig/fancontrol because of the missing hwmon sysfs entry
for actual revolutions per minute. This series adds this feature.
Changes in V2:
- address Guenter's comments:
- improve description of interrupts
- use atomic_t to avoid races of the pulse counter
- measure sample time to make rpm more reliable under load
- make sysfs entry fan1_input conditional
- add dt-property to define interrupts per fan revolution
- example for fan with RPM support
Stefan Wahren (3):
dt-bindings: hwmon: Add tachometer interrupt to pwm-fan
Documentation: pwm-fan: Add description for RPM support
hwmon: pwm-fan: Add RPM support via external interrupt
.../devicetree/bindings/hwmon/pwm-fan.txt | 19 +++++
Documentation/hwmon/pwm-fan | 3 +
drivers/hwmon/pwm-fan.c | 94 +++++++++++++++++++++-
3 files changed, 115 insertions(+), 1 deletion(-)
--
2.7.4
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 <[email protected]>
---
drivers/hwmon/pwm-fan.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 93 insertions(+), 1 deletion(-)
diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 167221c..0bacaba 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;
+ u32 pulse_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;
+
+ /* Avoid possible overflow */
+ if (atomic_read(&ctx->pulses) < 100000)
+ 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, sample_ms;
+
+ pulses = atomic_read(&ctx->pulses);
+ atomic_sub(pulses, &ctx->pulses);
+ sample_ms = ktime_ms_delta(ktime_get(), ctx->sample_start);
+ ctx->rpm = pulses * 60 * sample_ms / 1000 / ctx->pulse_per_revolution;
+
+ 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 +136,49 @@ 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 (devattr == &sensor_dev_attr_fan1_input.dev_attr) {
+ if (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,
@@ -261,6 +331,26 @@ static int pwm_fan_probe(struct platform_device *pdev)
goto err_reg_disable;
}
+ timer_setup(&ctx->rpm_timer, sample_timer, 0);
+
+ if (of_property_read_u32(pdev->dev.of_node, "interrupt-ratio",
+ &ctx->pulse_per_revolution)) {
+ ctx->pulse_per_revolution = 2;
+ }
+
+ atomic_set(&ctx->pulses, 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;
+ }
+ 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)) {
@@ -306,6 +396,8 @@ 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
This adds the tachometer interrupt to the pwm-fan binding, which is
necessary for RPM support.
Signed-off-by: Stefan Wahren <[email protected]>
---
Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
index 49ca5d8..7d09623 100644
--- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
+++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
@@ -8,6 +8,14 @@ Required properties:
Optional properties:
- fan-supply : phandle to the regulator that provides power to the fan
+- interrupts : This contains a single interrupt specifier which
+ describes the tachometer output of the fan as an
+ interrupt source. The output signal must generate a
+ defined number of interrupts per fan revolution, which
+ require that it must be self resetting edge interrupts.
+ See interrupt-controller/interrupts.txt for the format.
+- interrupt-ratio : defines the ratio interrupts per fan revolution as an
+ integer (default is 2 interrupts per revolution)
Example:
fan0: pwm-fan {
@@ -38,3 +46,14 @@ Example:
};
};
};
+
+Example 2:
+ fan0: pwm-fan {
+ fan0: pwm-fan {
+ compatible = "pwm-fan";
+ pwms = <&pwm 0 40000 0>;
+ fan-supply = <®_fan>;
+ interrupt-parent = <&gpio5>;
+ interrupts = <1 IRQ_TYPE_EDGE_FALLING>;
+ interrupt-ratio = <2>;
+ };
--
2.7.4
This adds a short description for the new RPM support of the pwm-fan
driver.
Signed-off-by: Stefan Wahren <[email protected]>
---
Documentation/hwmon/pwm-fan | 3 +++
1 file changed, 3 insertions(+)
diff --git a/Documentation/hwmon/pwm-fan b/Documentation/hwmon/pwm-fan
index 18529d2..82fe967 100644
--- a/Documentation/hwmon/pwm-fan
+++ b/Documentation/hwmon/pwm-fan
@@ -15,3 +15,6 @@ The driver implements a simple interface for driving a fan connected to
a PWM output. It uses the generic PWM interface, thus it can be used with
a range of SoCs. The driver exposes the fan to the user space through
the hwmon's sysfs interface.
+
+The fan rotation speed returned via the optional 'fan1_input' is extrapolated
+from the sampled interrupts from the tachometer signal within 1 second.
--
2.7.4
On Mon, Feb 25, 2019 at 04:59:17PM +0100, Stefan Wahren wrote:
> This adds the tachometer interrupt to the pwm-fan binding, which is
> necessary for RPM support.
>
> Signed-off-by: Stefan Wahren <[email protected]>
> ---
> Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> index 49ca5d8..7d09623 100644
> --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> @@ -8,6 +8,14 @@ Required properties:
>
> Optional properties:
> - fan-supply : phandle to the regulator that provides power to the fan
> +- interrupts : This contains a single interrupt specifier which
> + describes the tachometer output of the fan as an
> + interrupt source. The output signal must generate a
> + defined number of interrupts per fan revolution, which
> + require that it must be self resetting edge interrupts.
> + See interrupt-controller/interrupts.txt for the format.
> +- interrupt-ratio : defines the ratio interrupts per fan revolution as an
> + integer (default is 2 interrupts per revolution)
Name this for what it is, not how it is used. Using 'interrupt' is
misleading that it is related to the interrupt binding.
'tach-pulse-per-rev' or something similar.
>
> Example:
> fan0: pwm-fan {
> @@ -38,3 +46,14 @@ Example:
> };
> };
> };
> +
> +Example 2:
> + fan0: pwm-fan {
> + fan0: pwm-fan {
> + compatible = "pwm-fan";
> + pwms = <&pwm 0 40000 0>;
> + fan-supply = <®_fan>;
> + interrupt-parent = <&gpio5>;
> + interrupts = <1 IRQ_TYPE_EDGE_FALLING>;
> + interrupt-ratio = <2>;
> + };
> --
> 2.7.4
>