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adt7470: make automatic fan control really work

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It turns out that the adt7470's automatic fan control algorithm only works
when the temperature sensors get updated.  This in turn happens only when
someone tells the chip to read its temperature sensors.  Regrettably, this
means that we have to drive the chip periodically.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Darrick J. Wong
2009-01-06 14:41:34 -08:00
committed by Linus Torvalds
parent 2f22d5dff6
commit 89fac11cb3
2 changed files with 142 additions and 33 deletions
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19
Documentation/hwmon/adt7470
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@@ -31,15 +31,11 @@ Each of the measured inputs (temperature, fan speed) has corresponding high/low
limit values. The ADT7470 will signal an ALARM if any measured value exceeds
either limit.
The ADT7470 DOES NOT sample all inputs continuously. A single pin on the
ADT7470 is connected to a multitude of thermal diodes, but the chip must be
instructed explicitly to read the multitude of diodes. If you want to use
automatic fan control mode, you must manually read any of the temperature
sensors or the fan control algorithm will not run. The chip WILL NOT DO THIS
AUTOMATICALLY; this must be done from userspace. This may be a bug in the chip
design, given that many other AD chips take care of this. The driver will not
read the registers more often than once every 5 seconds. Further,
configuration data is only read once per minute.
The ADT7470 samples all inputs continuously. A kernel thread is started up for
the purpose of periodically querying the temperature sensors, thus allowing the
automatic fan pwm control to set the fan speed. The driver will not read the
registers more often than once every 5 seconds. Further, configuration data is
only read once per minute.
Special Features
----------------
@@ -72,5 +68,6 @@ pwm#_auto_point2_temp.
Notes
-----
As stated above, the temperature inputs must be read periodically from
userspace in order for the automatic pwm algorithm to run.
The temperature inputs no longer need to be read periodically from userspace in
order for the automatic pwm algorithm to run. This was the case for earlier
versions of the driver.