From 1814c4e84de2a89d1c2e1e9bbd241240561075a4 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Wed, 26 May 2021 08:40:21 -0700 Subject: [PATCH] hwmon: (max31790) Detect and report zero fan speed MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Václav Kubernát Signed-off-by: Guenter Roeck Tested-by: Václav Kubernát Link: https://lore.kernel.org/r/20210526154022.3223012-7-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 7927468c52715..7e9362f6dc29e 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) @@ -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: -- 2.30.2