drm/nouveau/doc: document the sysfs thermal management interface

Signed-off-by: Martin Peres <martin.peres@labri.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 81 insertions, 0 deletions

diff --git a/Documentation/thermal/nouveau_thermal b/Documentation/thermal/nouveau_thermal
new file mode 100644
index 00000000000..ec854fd3205
--- /dev/null
+++ b/Documentation/thermal/nouveau_thermal
@@ -0,0 +1,81 @@
+Kernel driver nouveau
+===================
+
+Supported chips:
+* NV43+
+
+Authors: Martin Peres (mupuf) <martin.peres@labri.fr>
+
+Description
+---------
+
+This driver allows to read the GPU core temperature, drive the GPU fan and
+set temperature alarms.
+
+Currently, due to the absence of in-kernel API to access HWMON drivers, Nouveau
+cannot access any of the i2c external monitoring chips it may find. If you
+have one of those, temperature and/or fan management through Nouveau's HWMON
+interface is likely not to work. This document may then not cover your situation
+entirely.
+
+Temperature management
+--------------------
+
+Temperature is exposed under as a read-only HWMON attribute temp1_input.
+
+In order to protect the GPU from overheating, Nouveau supports 4 configurable
+temperature thresholds:
+
+ * Fan_boost: Fan speed is set to 100% when reaching this temperature;
+ * Downclock: The GPU will be downclocked to reduce its power dissipation;
+ * Critical: The GPU is put on hold to further lower power dissipation;
+ * Shutdown: Shut the computer down to protect your GPU.
+
+WARNING: Some of these thresholds may not be used by Nouveau depending
+on your chipset.
+
+The default value for these thresholds comes from the GPU's vbios. These
+thresholds can be configured thanks to the following HWMON attributes:
+
+ * Fan_boost: temp1_auto_point1_temp and temp1_auto_point1_temp_hyst;
+ * Downclock: temp1_max and temp1_max_hyst;
+ * Critical: temp1_crit and temp1_crit_hyst;
+ * Shutdown: temp1_emergency and temp1_emergency_hyst.
+
+NOTE: Remember that the values are stored as milli degrees Celcius. Don't forget
+to multiply!
+
+Fan management
+------------
+
+Not all cards have a drivable fan. If you do, then the following HWMON
+attributes should be available:
+
+ * pwm1_enable: Current fan management mode (NONE, MANUAL or AUTO);
+ * pwm1: Current PWM value (power percentage);
+ * pwm1_min: The minimum PWM speed allowed;
+ * pwm1_max: The maximum PWM speed allowed (bypassed when hitting Fan_boost);
+
+You may also have the following attribute:
+
+ * fan0_input: Speed in RPM of your fan.
+
+Your fan can be driven in different modes:
+
+ * 0: The fan is left untouched;
+ * 1: The fan can be driven in manual (use pwm1 to change the speed);
+ * 2; The fan is driven automatically depending on the temperature.
+
+NOTE: Be sure to use the manual mode if you want to drive the fan speed manually
+
+NOTE2: Not all fan management modes may be supported on all chipsets. We are
+working on it.
+
+Bug reports
+---------
+
+Thermal management on Nouveau is new and may not work on all cards. If you have
+inquiries, please ping mupuf on IRC (#nouveau, freenode).
+
+Bug reports should be filled on Freedesktop's bug tracker. Please follow
+http://nouveau.freedesktop.org/wiki/Bugs