[PATCH V4 0/3] hwmon: pwm-fan: Add RPM support

[PATCH V4 0/3] hwmon: pwm-fan: Add RPM support

[Stefan Wahren]

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 V4:
- remove copy & paste artifact in dt-binding example
- switch to u64 for rpm calculation
- drop overflow handling and init atomic
- handle 0 not as valid irq
- reduce range of pulses_per_revolution
- handle probe defer of platform_get_irq
- delete timer properly in bail-out path

Changes in V3:
- rename property interrupt-ratio to pulses-per-revolution
  to avoid confusion with interrupt binding
- handle error case pulses-per-revolution = 0
- bail out properly in case we are unable to request the irq

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          |  21 +++-
 Documentation/hwmon/pwm-fan                        |   3 +
 drivers/hwmon/pwm-fan.c                            | 111 ++++++++++++++++++++-
 3 files changed, 130 insertions(+), 5 deletions(-)

-- 
2.7.4

[PATCH V4 1/3] dt-bindings: hwmon: Add tachometer interrupt to pwm-fan

[Stefan Wahren]

This adds the tachometer interrupt to the pwm-fan binding, which is
necessary for RPM support.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
 Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
index 49ca5d8..6ced829b 100644
--- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
+++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
@@ -7,7 +7,16 @@ Required properties:
 			which correspond to thermal cooling states
 
 Optional properties:
-- fan-supply    : phandle to the regulator that provides power to the fan
+- 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.
+- pulses-per-revolution : define the tachometer pulses per fan revolution as
+			  an integer (default is 2 interrupts per revolution).
+			  The value must be greater than zero.
 
 Example:
 	fan0: pwm-fan {
@@ -38,3 +47,13 @@ Example:
 					};
 			     };
 		};
+
+Example 2:
+	fan0: pwm-fan {
+		compatible = "pwm-fan";
+		pwms = <&pwm 0 40000 0>;
+		fan-supply = <&reg_fan>;
+		interrupt-parent = <&gpio5>;
+		interrupts = <1 IRQ_TYPE_EDGE_FALLING>;
+		pulses-per-revolution = <2>;
+	};
-- 
2.7.4

[PATCH V4 2/3] Documentation: pwm-fan: Add description for RPM support

[Stefan Wahren]

This adds a short description for the new RPM support of the pwm-fan
driver.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
---
 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

[PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt

[Stefan Wahren]

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 | 111 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 107 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 167221c..3245a49 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 +136,49 @@ 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,
@@ -261,17 +331,45 @@ 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_u8(pdev->dev.of_node, "pulses-per-revolution",
+				&ctx->pulses_per_revolution)) {
+		ctx->pulses_per_revolution = 2;
+	}
+
+	if (!ctx->pulses_per_revolution) {
+		dev_err(&pdev->dev, "pulses-per-revolution can't be zero.\n");
+		ret = -EINVAL;
+		goto err_pwm_disable;
+	}
+
+	ctx->irq = platform_get_irq(pdev, 0);
+	if (ctx->irq == -EPROBE_DEFER) {
+		ret = ctx->irq;
+		goto err_pwm_disable;
+	} else 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)
-		return ret;
+		goto err_del_timer;
 
 	ctx->pwm_fan_state = ctx->pwm_fan_max_state;
 	if (IS_ENABLED(CONFIG_THERMAL)) {
@@ -282,7 +380,7 @@ 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 +388,9 @@ 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 +407,8 @@ 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

Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt

[Guenter Roeck]

On Tue, Apr 02, 2019 at 04:21:50PM +0200, Stefan Wahren wrote:
> 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 | 111 ++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 107 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> index 167221c..3245a49 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 +136,49 @@ 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;
> +	}

Side note: This can be easier written as 
	if (n == 1 && ctx->irq <= 0)
		return 0;

Not that it matters much.

> +
> +	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,
> @@ -261,17 +331,45 @@ 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_u8(pdev->dev.of_node, "pulses-per-revolution",

This does not work: The property is not defined as u8. You have to either
use of_property_read_u32() or declare the property as u8.

[ Sorry, I didn't know until recently that this is necessary ]

> +				&ctx->pulses_per_revolution)) {
> +		ctx->pulses_per_revolution = 2;
> +	}
> +
> +	if (!ctx->pulses_per_revolution) {
> +		dev_err(&pdev->dev, "pulses-per-revolution can't be zero.\n");
> +		ret = -EINVAL;
> +		goto err_pwm_disable;
> +	}
> +
> +	ctx->irq = platform_get_irq(pdev, 0);
> +	if (ctx->irq == -EPROBE_DEFER) {
> +		ret = ctx->irq;
> +		goto err_pwm_disable;

It might be better to call platform_get_irq() and to do do this check
first, before enabling the regulator (in practice before calling
devm_regulator_get_optional). It doesn't make sense to enable the
regulator only to disable it because the irq is not yet available.

> +	} else if (ctx->irq > 0) {

As written, this else is unnecessary, and static checkers will complain
about it.

> +		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)
> -		return ret;
> +		goto err_del_timer;

Outch. This is buggy and should have been "goto err_pwm_disable;".
It needs to be fixed with a separate patch, and first, so we can
backport it. Can you do that ?

>  
>  	ctx->pwm_fan_state = ctx->pwm_fan_max_state;
>  	if (IS_ENABLED(CONFIG_THERMAL)) {
> @@ -282,7 +380,7 @@ 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 +388,9 @@ 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 +407,8 @@ 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
> 

Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt

[Stefan Wahren]

Hi Guenter,

Am 02.04.19 um 22:55 schrieb Guenter Roeck:
> On Tue, Apr 02, 2019 at 04:21:50PM +0200, Stefan Wahren wrote:
>> 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 | 111 ++++++++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 107 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
>> index 167221c..3245a49 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 +136,49 @@ 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;
>> +	}
> Side note: This can be easier written as 
> 	if (n == 1 && ctx->irq <= 0)
> 		return 0;
>
> Not that it matters much.
>
>> +
>> +	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,
>> @@ -261,17 +331,45 @@ 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_u8(pdev->dev.of_node, "pulses-per-revolution",
> This does not work: The property is not defined as u8. You have to either
> use of_property_read_u32() or declare the property as u8.
pulses_per_revolution is defined as u8 since this version
>
> [ Sorry, I didn't know until recently that this is necessary ]
>
>> +				&ctx->pulses_per_revolution)) {
>> +		ctx->pulses_per_revolution = 2;
>> +	}
>> +
>> +	if (!ctx->pulses_per_revolution) {
>> +		dev_err(&pdev->dev, "pulses-per-revolution can't be zero.\n");
>> +		ret = -EINVAL;
>> +		goto err_pwm_disable;
>> +	}
>> +
>> +	ctx->irq = platform_get_irq(pdev, 0);
>> +	if (ctx->irq == -EPROBE_DEFER) {
>> +		ret = ctx->irq;
>> +		goto err_pwm_disable;
> It might be better to call platform_get_irq() and to do do this check
> first, before enabling the regulator (in practice before calling
> devm_regulator_get_optional). It doesn't make sense to enable the
> regulator only to disable it because the irq is not yet available.
>
>> +	} else if (ctx->irq > 0) {
> As written, this else is unnecessary, and static checkers will complain
> about it.
>
>> +		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)
>> -		return ret;
>> +		goto err_del_timer;
> Outch. This is buggy and should have been "goto err_pwm_disable;".
> It needs to be fixed with a separate patch, and first, so we can
> backport it. Can you do that ?

Sure

Stefan

Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt

[Robin Murphy]

On 03/04/2019 10:55, Stefan Wahren wrote:
> Hi Guenter,
> 
> Am 02.04.19 um 22:55 schrieb Guenter Roeck:
>> On Tue, Apr 02, 2019 at 04:21:50PM +0200, Stefan Wahren wrote:
>>> 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 | 111 ++++++++++++++++++++++++++++++++++++++++++++++--
>>>   1 file changed, 107 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
>>> index 167221c..3245a49 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 +136,49 @@ 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;
>>> +	}
>> Side note: This can be easier written as
>> 	if (n == 1 && ctx->irq <= 0)
>> 		return 0;
>>
>> Not that it matters much.
>>
>>> +
>>> +	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,
>>> @@ -261,17 +331,45 @@ 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_u8(pdev->dev.of_node, "pulses-per-revolution",
>> This does not work: The property is not defined as u8. You have to either
>> use of_property_read_u32() or declare the property as u8.
> pulses_per_revolution is defined as u8 since this version

The variable might be, but the "pulses-per-revolution" property itself 
is not being defined with the appropriate DT type ("/bits/ 8") in the 
binding, and thus will be stored as a regular 32-bit cell, for which 
reading it as a u8 array may or may not work correctly depending on 
endianness.

TBH, unless there's a real need for a specific binary format in the FDT, 
I don't think it's usually worth the bother of using irregular DT types, 
especially when the practical impact amounts to possibly saving up to 3 
bytes for a property which usually won't need to be specified anyway. 
I'd just do something like:

	u32 ppr = 2;

	of_property_read_u32(np, "pulses-per-revolution", &ppr);
	ctx->pulses_per_revolution = ppr;

>>
>> [ Sorry, I didn't know until recently that this is necessary ]
>>
>>> +				&ctx->pulses_per_revolution)) {
>>> +		ctx->pulses_per_revolution = 2;
>>> +	}
>>> +
>>> +	if (!ctx->pulses_per_revolution) {
>>> +		dev_err(&pdev->dev, "pulses-per-revolution can't be zero.\n");
>>> +		ret = -EINVAL;
>>> +		goto err_pwm_disable;
>>> +	}
>>> +
>>> +	ctx->irq = platform_get_irq(pdev, 0);
>>> +	if (ctx->irq == -EPROBE_DEFER) {
>>> +		ret = ctx->irq;
>>> +		goto err_pwm_disable;
>> It might be better to call platform_get_irq() and to do do this check
>> first, before enabling the regulator (in practice before calling
>> devm_regulator_get_optional). It doesn't make sense to enable the
>> regulator only to disable it because the irq is not yet available.
>>
>>> +	} else if (ctx->irq > 0) {
>> As written, this else is unnecessary, and static checkers will complain
>> about it.
>>
>>> +		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;

We could still continue without RPM support at this point, couldn't we? 
Or is this a deliberate "if that failed, then who knows how messed up 
the system is..." kind of thing?

Robin.

>>> +		}
>>> +		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)
>>> -		return ret;
>>> +		goto err_del_timer;
>> Outch. This is buggy and should have been "goto err_pwm_disable;".
>> It needs to be fixed with a separate patch, and first, so we can
>> backport it. Can you do that ?
> 
> Sure
> 
> Stefan
> 

Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt

[Guenter Roeck]

On Wed, Apr 03, 2019 at 04:59:35PM +0100, Robin Murphy wrote:
> On 03/04/2019 10:55, Stefan Wahren wrote:
> >Hi Guenter,
> >
> >Am 02.04.19 um 22:55 schrieb Guenter Roeck:
> >>On Tue, Apr 02, 2019 at 04:21:50PM +0200, Stefan Wahren wrote:
> >>>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 | 111 ++++++++++++++++++++++++++++++++++++++++++++++--
> >>>  1 file changed, 107 insertions(+), 4 deletions(-)
> >>>
> >>>diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> >>>index 167221c..3245a49 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 +136,49 @@ 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;
> >>>+	}
> >>Side note: This can be easier written as
> >>	if (n == 1 && ctx->irq <= 0)
> >>		return 0;
> >>
> >>Not that it matters much.
> >>
> >>>+
> >>>+	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,
> >>>@@ -261,17 +331,45 @@ 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_u8(pdev->dev.of_node, "pulses-per-revolution",
> >>This does not work: The property is not defined as u8. You have to either
> >>use of_property_read_u32() or declare the property as u8.
> >pulses_per_revolution is defined as u8 since this version
> 
> The variable might be, but the "pulses-per-revolution" property itself is
> not being defined with the appropriate DT type ("/bits/ 8") in the binding,
> and thus will be stored as a regular 32-bit cell, for which reading it as a
> u8 array may or may not work correctly depending on endianness.
> 
> TBH, unless there's a real need for a specific binary format in the FDT, I
> don't think it's usually worth the bother of using irregular DT types,
> especially when the practical impact amounts to possibly saving up to 3
> bytes for a property which usually won't need to be specified anyway. I'd
> just do something like:
> 
> 	u32 ppr = 2;
> 
> 	of_property_read_u32(np, "pulses-per-revolution", &ppr);
> 	ctx->pulses_per_revolution = ppr;
> 

+1

Thanks,
Guenter

> >>
> >>[ Sorry, I didn't know until recently that this is necessary ]
> >>
> >>>+				&ctx->pulses_per_revolution)) {
> >>>+		ctx->pulses_per_revolution = 2;
> >>>+	}
> >>>+
> >>>+	if (!ctx->pulses_per_revolution) {
> >>>+		dev_err(&pdev->dev, "pulses-per-revolution can't be zero.\n");
> >>>+		ret = -EINVAL;
> >>>+		goto err_pwm_disable;
> >>>+	}
> >>>+
> >>>+	ctx->irq = platform_get_irq(pdev, 0);
> >>>+	if (ctx->irq == -EPROBE_DEFER) {
> >>>+		ret = ctx->irq;
> >>>+		goto err_pwm_disable;
> >>It might be better to call platform_get_irq() and to do do this check
> >>first, before enabling the regulator (in practice before calling
> >>devm_regulator_get_optional). It doesn't make sense to enable the
> >>regulator only to disable it because the irq is not yet available.
> >>
> >>>+	} else if (ctx->irq > 0) {
> >>As written, this else is unnecessary, and static checkers will complain
> >>about it.
> >>
> >>>+		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;
> 
> We could still continue without RPM support at this point, couldn't we? Or
> is this a deliberate "if that failed, then who knows how messed up the
> system is..." kind of thing?
> 
> Robin.
> 
> >>>+		}
> >>>+		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)
> >>>-		return ret;
> >>>+		goto err_del_timer;
> >>Outch. This is buggy and should have been "goto err_pwm_disable;".
> >>It needs to be fixed with a separate patch, and first, so we can
> >>backport it. Can you do that ?
> >
> >Sure
> >
> >Stefan
> >

Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt

[Stefan Wahren]

Am 03.04.2019 um 17:59 schrieb Robin Murphy:
> On 03/04/2019 10:55, Stefan Wahren wrote:
>> Hi Guenter,
>>
>> Am 02.04.19 um 22:55 schrieb Guenter Roeck:
>>> On Tue, Apr 02, 2019 at 04:21:50PM +0200, Stefan Wahren wrote:
>>>> 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 | 111 
>>>> ++++++++++++++++++++++++++++++++++++++++++++++--
>>>>   1 file changed, 107 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
>>>> index 167221c..3245a49 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 +136,49 @@ 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;
>>>> +    }
>>> Side note: This can be easier written as
>>>     if (n == 1 && ctx->irq <= 0)
>>>         return 0;
>>>
>>> Not that it matters much.
>>>
>>>> +
>>>> +    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,
>>>> @@ -261,17 +331,45 @@ 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_u8(pdev->dev.of_node, 
>>>> "pulses-per-revolution",
>>> This does not work: The property is not defined as u8. You have to 
>>> either
>>> use of_property_read_u32() or declare the property as u8.
>> pulses_per_revolution is defined as u8 since this version
>
> The variable might be, but the "pulses-per-revolution" property itself 
> is not being defined with the appropriate DT type ("/bits/ 8") in the 
> binding, and thus will be stored as a regular 32-bit cell, for which 
> reading it as a u8 array may or may not work correctly depending on 
> endianness.
>
> TBH, unless there's a real need for a specific binary format in the 
> FDT, I don't think it's usually worth the bother of using irregular DT 
> types, especially when the practical impact amounts to possibly saving 
> up to 3 bytes for a property which usually won't need to be specified 
> anyway. I'd just do something like:
>
>     u32 ppr = 2;
>
>     of_property_read_u32(np, "pulses-per-revolution", &ppr);
>     ctx->pulses_per_revolution = ppr;

My intention was to avoid another overflow in case the device tree 
provides unrealistic values ( my expected range 1 - 10 ). Saving space 
would be a benefit, but i'm okay with this suggestion.

>
>>>
>>> [ Sorry, I didn't know until recently that this is necessary ]
>>>
>>>> + &ctx->pulses_per_revolution)) {
>>>> +        ctx->pulses_per_revolution = 2;
>>>> +    }
>>>> +
>>>> +    if (!ctx->pulses_per_revolution) {
>>>> +        dev_err(&pdev->dev, "pulses-per-revolution can't be 
>>>> zero.\n");
>>>> +        ret = -EINVAL;
>>>> +        goto err_pwm_disable;
>>>> +    }
>>>> +
>>>> +    ctx->irq = platform_get_irq(pdev, 0);
>>>> +    if (ctx->irq == -EPROBE_DEFER) {
>>>> +        ret = ctx->irq;
>>>> +        goto err_pwm_disable;
>>> It might be better to call platform_get_irq() and to do do this check
>>> first, before enabling the regulator (in practice before calling
>>> devm_regulator_get_optional). It doesn't make sense to enable the
>>> regulator only to disable it because the irq is not yet available.
>>>
>>>> +    } else if (ctx->irq > 0) {
>>> As written, this else is unnecessary, and static checkers will complain
>>> about it.
>>>
>>>> +        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;
>
> We could still continue without RPM support at this point, couldn't 
> we? Or is this a deliberate "if that failed, then who knows how messed 
> up the system is..." kind of thing?

In case someone specified an interrupt, the user expect it to work. This 
helps to identify broken DT faster.

The gpio-fan also have optional irq support and also bail out if 
devm_request_irq fails.

Btw i will add the return code into the error message.

Stefan