ACPI: ibm-acpi: fix and extend fan control functions
This patch extend fan control functions, implementing enable/disable for
all write access modes, implementing level control for all level-capable
write access modes.
The patch also updates the documentation, explaining levels auto and
disengaged.
ABI changes:
1. Support level 0 as an equivalent to disable
2. Add support for level auto and level disengaged when doing
EC 0x2f fan control
3. Support enable/disable for all level-based write access modes
4. Add support for level command on FANS thinkpads, as per
thinkwiki reports
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
diff --git a/Documentation/ibm-acpi.txt b/Documentation/ibm-acpi.txt
index 333b8eb..cbd3a60 100644
--- a/Documentation/ibm-acpi.txt
+++ b/Documentation/ibm-acpi.txt
@@ -571,27 +571,57 @@
WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.
-This feature attempts to show the current fan speed. The speed is read
-directly from the hardware registers of the embedded controller. This
-is known to work on later R, T and X series ThinkPads but may show a
-bogus value on other models.
+This feature attempts to show the current fan speed, control mode and
+other fan data that might be available. The speed is read directly
+from the hardware registers of the embedded controller. This is known
+to work on later R, T and X series ThinkPads but may show a bogus
+value on other models.
+
+Most ThinkPad fans work in "levels". Level 0 stops the fan. The higher
+the level, the higher the fan speed, although adjacent levels often map
+to the same fan speed. 7 is the highest level, where the fan reaches
+the maximum recommended speed. Level "auto" means the EC changes the
+fan level according to some internal algorithm, usually based on
+readings from the thermal sensors. Level "disengaged" means the EC
+disables the speed-locked closed-loop fan control, and drives the fan as
+fast as it can go, which might exceed hardware limits, so use this level
+with caution.
+
+The fan usually ramps up or down slowly from one speed to another,
+and it is normal for the EC to take several seconds to react to fan
+commands.
The fan may be enabled or disabled with the following commands:
echo enable >/proc/acpi/ibm/fan
echo disable >/proc/acpi/ibm/fan
-WARNING WARNING WARNING: do not leave the fan disabled unless you are
-monitoring the temperature sensor readings and you are ready to enable
-it if necessary to avoid overheating.
+Placing a fan on level 0 is the same as disabling it. Enabling a fan
+will try to place it in a safe level if it is too slow or disabled.
-The fan only runs if it's enabled *and* the various temperature
-sensors which control it read high enough. On the X40, this seems to
-depend on the CPU and HDD temperatures. Specifically, the fan is
-turned on when either the CPU temperature climbs to 56 degrees or the
-HDD temperature climbs to 46 degrees. The fan is turned off when the
-CPU temperature drops to 49 degrees and the HDD temperature drops to
-41 degrees. These thresholds cannot currently be controlled.
+WARNING WARNING WARNING: do not leave the fan disabled unless you are
+monitoring all of the temperature sensor readings and you are ready to
+enable it if necessary to avoid overheating.
+
+An enabled fan in level "auto" may stop spinning if the EC decides the
+ThinkPad is cool enough and doesn't need the extra airflow. This is
+normal, and the EC will spin the fan up if the varios thermal readings
+rise too much.
+
+On the X40, this seems to depend on the CPU and HDD temperatures.
+Specifically, the fan is turned on when either the CPU temperature
+climbs to 56 degrees or the HDD temperature climbs to 46 degrees. The
+fan is turned off when the CPU temperature drops to 49 degrees and the
+HDD temperature drops to 41 degrees. These thresholds cannot
+currently be controlled.
+
+The fan level can be controlled with the command:
+
+ echo 'level <level>' > /proc/acpi/ibm/thermal
+
+Where <level> is an integer from 0 to 7, or one of the words "auto"
+or "disengaged" (without the quotes). Not all ThinkPads support the
+"auto" and "disengaged" levels.
On the X31 and X40 (and ONLY on those models), the fan speed can be
controlled to a certain degree. Once the fan is running, it can be
@@ -604,12 +634,9 @@
any effect or the fan speed eventually settles somewhere in that
range. The fan cannot be stopped or started with this command.
-On the 570, temperature readings are not available through this
-feature and the fan control works a little differently. The fan speed
-is reported in levels from 0 (off) to 7 (max) and can be controlled
-with the following command:
-
- echo 'level <level>' > /proc/acpi/ibm/thermal
+The ThinkPad's ACPI DSDT code will reprogram the fan on its own when
+certain conditions are met. It will override any fan programming done
+through ibm-acpi.
EXPERIMENTAL: WAN -- /proc/acpi/ibm/wan
---------------------------------------