Re: [PATCH v1 4/4] hwmon: add driver for the Microchip LAN966x SoC

[Michael Walle]

Am 2022-03-27 03:34, schrieb Guenter Roeck:

> > +	/*
> > +	 * Data is given in pulses per second. According to the hwmon ABI we
> > +	 * have to assume two pulses per revolution.
>
> The hwmon ABI doesn't make any such assumptions. It wants to see RPM,
> that is all. Pulses per revolution is a fan property.

There is fanY_pulses according to 
Documentation/ABI/testing/sysfs-class-hwmon:

  Should only be created if the chip has a register to configure
  the number of pulses. In the absence of such a register (and
  thus attribute) the value assumed by all devices is 2 pulses
  per fan revolution.

The hardware returns just the pulses per second. Doesn't that
mean I have to divide that value by two?

> > +	 */
> > +	*val = FIELD_GET(FAN_CNT_DATA, data) * 60 / 2;

.. otherwise this should then be
*val = FIELD_GET(FAN_CNT_DATA, data) * 60;


> > +
> > +	return 0;
> > +}
> > +
> > +static int lan966x_hwmon_read_pwm(struct device *dev, long *val)
> > +{
> > +	struct lan966x_hwmon *hwmon = dev_get_drvdata(dev);
> > +	unsigned int data;
> > +	int ret;
> > +
> > +	ret = regmap_read(hwmon->regmap_fan, FAN_CFG, &data);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	*val = FIELD_GET(FAN_CFG_DUTY_CYCLE, data);
> > +
> > +	return 0;
> > +}
> > +
> > +static int lan966x_hwmon_read_pwm_freq(struct device *dev, long *val)
> > +{
> > +	struct lan966x_hwmon *hwmon = dev_get_drvdata(dev);
> > +	unsigned long rate = clk_get_rate(hwmon->clk);
>
> Is that a dynamic frequency ? If not, it would be better to read it 
> once
> and store it in struct lan966x_hwmon.

yes it is configurable, actually. See lan966x_hwmon_write_pwm_freq().

-michael