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authorGuenter Roeck <linux@roeck-us.net>2020-08-08 18:07:10 -0700
committerGuenter Roeck <linux@roeck-us.net>2020-09-23 09:42:39 -0700
commite40358390928f9ab9d8d7dde5c60c08981dc1d81 (patch)
tree02d868700b3a2bcac73edea09b05e50d07474fda /Documentation/hwmon
parent787c095edaa9de28d39671282eba7bddd479c038 (diff)
hwmon: (drivetemp) Add usage not describing impact on drive spin-down
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@sulyok.net> Cc: Peter Sulyok <peter@sulyok.net> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Diffstat (limited to 'Documentation/hwmon')
-rw-r--r--Documentation/hwmon/drivetemp.rst18
1 files changed, 18 insertions, 0 deletions
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
-------------