path: root/Documentation/laptops
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authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2009-06-18 00:40:17 -0300
committerLen Brown <len.brown@intel.com>2009-06-18 01:30:57 -0400
commitd73772474f6ebbacbe820c31c0fa1cffa7160246 (patch)
tree7564212618d43910de01a818c0cdef5759ad12a9 /Documentation/laptops
parentd7880f10c5d42ba182a97c1fd41d41d0b8837097 (diff)
thinkpad-acpi: support the second fan on the X61
Support reading the tachometer of the auxiliary fan of a X60/X61. It was found out by sheer luck, that bit 0 of EC register 0x31 (formely HBRV) selects which fan is active for tachometer readings through EC 0x84/0x085: 0 for fan1, 1 for fan2. Many thanks to Christoph Kl??nter, to Whoopie, and to weasel, who helped confirm that behaviour. Fan control through EC HFSP applies to both fans equally, regardless of the state of bit 0 of EC 0x31. That matches the way the DSDT uses HFSP. In order to better support the secondary fan, export a second tachometer over hwmon, and add defensive measures to make sure we are reading the correct tachometer. Support for the second fan is whitelist-based, as I have not found anything obvious to look for in the DSDT to detect the presence of the second fan. Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/laptops')
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index f2ff638cce8d..0d5e91379ae8 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1269,7 +1269,7 @@ Fan control and monitoring: fan speed, fan enable/disable
procfs: /proc/acpi/ibm/fan
sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1,
- pwm1_enable
+ pwm1_enable, fan2_input
sysfs hwmon driver attributes: fan_watchdog
NOTE NOTE NOTE: fan control operations are disabled by default for
@@ -1282,6 +1282,9 @@ from the hardware registers of the embedded controller. This is known
to work on later R, T, X and Z series ThinkPads but may show a bogus
value on other models.
+Some Lenovo ThinkPads support a secondary fan. This fan cannot be
+controlled separately, it shares the main fan control.
Fan levels:
Most ThinkPad fans work in "levels" at the firmware interface. Level 0
@@ -1412,6 +1415,11 @@ hwmon device attribute fan1_input:
which can take up to two minutes. May return rubbish on older
+hwmon device attribute fan2_input:
+ Fan tachometer reading, in RPM, for the secondary fan.
+ Available only on some ThinkPads. If the secondary fan is
+ not installed, will always read 0.
hwmon driver attribute fan_watchdog:
Fan safety watchdog timer interval, in seconds. Minimum is
1 second, maximum is 120 seconds. 0 disables the watchdog.

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