Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt
From: Robin Murphy
Date: Wed Apr 03 2019 - 11:59:42 EST
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@xxxxxxxx>
---
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