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Message-ID: <20190403161142.GA10544@roeck-us.net>
Date: Wed, 3 Apr 2019 09:11:42 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Robin Murphy <robin.murphy@....com>
Cc: Stefan Wahren <stefan.wahren@...e.com>,
Kamil Debski <kamil@...as.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
Jean Delvare <jdelvare@...e.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 3/3] hwmon: pwm-fan: Add RPM support via external
interrupt
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@...e.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
> >
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