Messages in this thread | | | Date | Mon, 28 Mar 2022 13:28:12 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v1 4/4] hwmon: add driver for the Microchip LAN966x SoC |
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Am 2022-03-27 20:22, schrieb Guenter Roeck: > On 3/27/22 07:18, Michael Walle wrote: >> 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? >> > > The above refers to hardware which reports RPM. > > It is up to the driver to calculate and return RPM. How you do it is > your > decision. Drivers should report the most likely correct RPM value to > userspace, one that rarely needs manual adjustment. Almost all fans > report two pulses per revolution, so normally that assumption is used > to convert PPM to RPM. That isn't mandated (or supposed to be mandated) > by the ABI. I would call it common sense. > > I'll be happy to accept a patch clarifying this.
Where would that go? into the sysfs abi description of the fanY_input?
>>>> + */ >>>> + *val = FIELD_GET(FAN_CNT_DATA, data) * 60 / 2; >> >> .. otherwise this should then be >> *val = FIELD_GET(FAN_CNT_DATA, data) * 60; >> > > If you really want to do this, make sure it is well documented that > users > will need to adjust the fan speed via sensors3.conf to get the real fan > speed. > >> >>>> + >>>> + 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(). >> > > That is the pwm frequency, not the clock frequency. I don't see any > code which updates the clock frequency reported by > clk_get_rate(hwmon->clk), > ie I don't see a call to clk_set_rate().
Ahh sorry, missunderstood you. Yeah, in v2 it will be read during probe.
-michael
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