Messages in this thread | | | Subject | Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external interrupt | From | Robin Murphy <> | Date | Wed, 3 Apr 2019 16:59:35 +0100 |
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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 >
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