mb/asus/p5q: Document working fan control and FireWire port

Fan control and FireWire work fine on my board.

Signed-off-by: Stefan Ott <stefan@ott.net>
Change-Id: Idc69e902370c4094daef93e843abc6ae564625f3
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51360
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

Documentation/mainboard/asus/p5q.md

@@ -2,9 +2,7 @@
 
 This page describes how to run coreboot on the [ASUS P5Q] desktop board.
 
-## TODO
-
-The following things are working in this coreboot port:
+## Working
 
 + PCI slots
 + PCI-e slots
@@ -15,20 +13,21 @@ The following things are working in this coreboot port:
 + All 4 DIMM slots
 + S3 suspend and resume
 + Red SATA ports
++ Fan control through the W83667HG chip
++ FireWire
 
-The following things are still missing from this coreboot port:
+## Not working
 
 + PS/2 mouse support
 + PATA aka IDE (because of buggy IDE controller)
-+ Fan control (will be working on 100% power)
++ Fan profiles with Q-Fan
 + TPM module (support not implemented)
 
-The following things are untested on this coreboot port:
+## Untested
 
 + S/PDIF
 + CD Audio In
 + Floppy disk drive
-+ FireWire: PCI device shows up and driver loads, no further test
 
 
 ## Flashing coreboot
@@ -73,5 +72,63 @@ You can flash coreboot into your motherboard using [this guide].
 +------------------+---------------------------------------------------+
 ```
 
+## Controlling fans
+
+With vendor firmware, the P5Q uses the ATK0110 ACPI device to control its fans
+according to the parameters configured in the BIOS setup menu. With coreboot,
+one can instead control the Super I/O directly as described in the
+[kernel docs]:
+
++ pwm1 controls fan1 (CHA_FAN1) and fan4 (CHA_FAN2)
++ pwm2 controls fan2 (CPU_FAN)
++ fan3 (PWR_FAN) cannot be controlled
++ temp1 (board) can be used to control fan1 and fan4
++ temp2 (CPU) can be used to control fan2
+
+### Manual fan speed
+
+These commands set the chassis fans to a constant speed:
+
+    # Use PWM output
+    echo 1 >/sys/class/hwmon/hwmon2/pwm1_mode
+    # Set to manual mode
+    echo 1 >/sys/class/hwmon/hwmon2/pwm1_enable
+    # Set relative speed: 0 (stop) to 255 (full)
+    echo 150 >/sys/class/hwmon/hwmon2/pwm1
+
+### Automatic fan speed
+
+The W83667HG can adjust fan speeds when things get too warm. These settings will
+control the chassis fans:
+
+    # Set to "Thermal Cruise" mode
+    echo 2 >/sys/class/hwmon/hwmon2/pwm1_enable
+    # Target temperature: 60°C
+    echo 60000 >/sys/class/hwmon/hwmon2/pwm1_target
+    # Minimum fan speed when spinning up
+    echo 135 >/sys/class/hwmon/hwmon2/pwm1_start_output
+    # Minimum fan speed when spinning down
+    echo 135 >/sys/class/hwmon/hwmon2/pwm1_stop_output
+    # Tolerance: 2°C
+    echo 2000 >/sys/class/hwmon/hwmon2/pwm1_tolerance
+    # Turn fans off after 600 seconds when below defined range
+    echo 600000 >/sys/class/hwmon/hwmon2/pwm1_stop_time
+
+You can also control the CPU fan with similar rules:
+
+    # Switch to "Thermal Cruise" mode
+    echo 2 >/sys/class/hwmon/hwmon2/pwm2_enable
+    # Target temperature: 55°C
+    echo 55000 >/sys/class/hwmon/hwmon2/pwm2_target
+    # Minimum fan speed when spinning down
+    echo 50 >/sys/class/hwmon/hwmon2/pwm2_stop_output
+    # Rate of fan speed change
+    echo 50 >/sys/class/hwmon/hwmon2/pwm2_step_output
+    # Maximum fan speed
+    echo 200 >/sys/class/hwmon/hwmon2/pwm2_max_output
+    # Tolerance: 2°C
+    echo 2000 >/sys/class/hwmon/hwmon2/pwm1_tolerance
+
 [ASUS P5Q]: https://www.asus.com/Motherboards/P5Q
 [this guide]: https://doc.coreboot.org/flash_tutorial/int_flashrom.html
+[kernel docs]: https://www.kernel.org/doc/Documentation/hwmon/w83627ehf.rst