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hwmon: (max31790) Detect and report zero fan speed

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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>
Tested-by: Václav Kubernát <kubernat@cesnet.cz>
Link: https://lore.kernel.org/r/20210526154022.3223012-7-linux@roeck-us.net
This commit is contained in:
Guenter Roeck 2021-05-26 08:40:21 -07:00
parent 2013607b85
commit 1814c4e84d
1 changed files with 6 additions and 1 deletions
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7
drivers/hwmon/max31790.c
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@ -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)
@ -172,7 +174,10 @@ 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]);
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: