Commit 1814c4e8 authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (max31790) Detect and report zero fan speed 



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: default avatarGuenter Roeck <linux@roeck-us.net>
Tested-by: default avatarVáclav Kubernát <kubernat@cesnet.cz>
Link: https://lore.kernel.org/r/20210526154022.3223012-7-linux@roeck-us.net
parent 2013607b

drivers/hwmon/max31790.c

+6 −1
Original line number Diff line number Diff line
@@ -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)
@@ -172,6 +174,9 @@ static int max31790_read_fan(struct device *dev, u32 attr, int channel, 
	switch (attr) {

	case hwmon_fan_input:

		sr = get_tach_period(data->fan_dynamics[channel % NR_CHANNEL]);

		if (data->tach[channel] == FAN_COUNT_REG_MAX)

			rpm = 0;

		else

			rpm = RPM_FROM_REG(data->tach[channel], sr);

		*val = rpm;

		return 0;