On some drives, reading the drive temperature resets the drive's spin-down timer. If the drive temperature is read too often, affected drives will never spin down. Add this information as usage note to the driver documentation. Reported-by: Peter Sulyok <peter@xxxxxxxxxx> Cc: Peter Sulyok <peter@xxxxxxxxxx> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx> --- Documentation/hwmon/drivetemp.rst | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/Documentation/hwmon/drivetemp.rst b/Documentation/hwmon/drivetemp.rst index 2d37d049247f..0b1cf2f912c5 100644 --- a/Documentation/hwmon/drivetemp.rst +++ b/Documentation/hwmon/drivetemp.rst @@ -30,6 +30,24 @@ Transport is not supported, the driver uses SMART attributes to read the drive temperature. +Usage Note +---------- + +Reading the drive temperature may reset the spin down timer on some drives. +This has been observed with WD120EFAX drives, but may be seen with other +drives as well. The same behavior is observed if the 'hdtemp' or 'smartd' +tools are used to access the drive. +With the WD120EFAX drive, reading the drive temperature using the drivetemp +driver is still possible _after_ it transitioned to standby mode, and +reading the drive temperature in this mode will not cause the drive to +change its mode (meaning the drive will not spin up). It is unknown if other +drives experience similar behavior. + +A known workaround for WD120EFAX drives is to read the drive temperature at +intervals larger than twice the spin-down time. Otherwise affected drives +will never spin down. + + Sysfs entries ------------- -- 2.17.1
