Re: [PATCH 6/7] hwmon: (max31790) Detect and report zero fan speed

Václav Kubernát
2021-06-01T08:11:28Z

Zero fan speed is reported correctly.

Tested-by: Václav Kubernát <kubernat@cesnet.cz>

st 26. 5. 2021 v 17:41 odesílatel Guenter Roeck <linux@roeck-us.net> napsal:
>
> If a fan is not running or not connected, of if fan monitoring is disabled,
> the fan count register returns a fixed value of 0xffe0. So far this is then
> translated to a RPM value larger than 0. Since this is misleading and does
> not really make much sense, report a fan RPM of 0 in this situation.
>
> Cc: Jan Kundrát <jan.kundrat@cesnet.cz>
> Cc: Václav Kubernát <kubernat@cesnet.cz>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> drivers/hwmon/max31790.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
> index 8e4fd9b7c889..91fe419b596c 100644
> --- a/drivers/hwmon/max31790.c
> +++ b/drivers/hwmon/max31790.c
> @@ -40,6 +40,8 @@
> #define FAN_RPM_MIN 120
> #define FAN_RPM_MAX 7864320
>
> +#define FAN_COUNT_REG_MAX 0xffe0
> +
> #define RPM_FROM_REG(reg, sr) (((reg) >> 4) ? \
> ((60 * (sr) * 8192) / ((reg) >> 4)) : \
> FAN_RPM_MAX)
> @@ -175,7 +177,10 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel,
> return 0;
> case hwmon_fan_input:
> sr = get_tach_period(data->fan_dynamics[channel % NR_CHANNEL]);
> - rpm = RPM_FROM_REG(data->tach[channel], sr);
> + if (data->tach[channel] == FAN_COUNT_REG_MAX)
> + rpm = 0;
> + else
> + rpm = RPM_FROM_REG(data->tach[channel], sr);
> *val = rpm;
> return 0;
> case hwmon_fan_target:
> --
> 2.25.1
>