ec/lenovo/h8/acpi/thermal: Add ACPI fan control

Disengage the fan 10 degree below passive threshold as the automatic EC fan
control does not disengage the FAN even when CPU starts melting ...

* Add EC registers FAND and FANA.
* Add ACPI methods _AC0 and _AL0.
* Add fan device and PowerResource for fan control.

Tested on Lenovo T430:
* The fan disengages at 80°C and keeps running at full speed until temperature
  drops below 80°C.
* Fan can be disengaged using sysfs:
  /sys/devics/virtual/thermal/cooling_device0/cur_state
Tested on Lenovo T500:
* The fan disengages at 80°C and keeps running at full speed until temperature
  drops below 80°C.
* Fan cannot be disengaged using sysfs, but the current state can be read:
  /sys/devics/virtual/thermal/cooling_device0/cur_state

Change-Id: I075ff5c69676927db1c5e731294e18796884f97e
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/21227
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/ec/lenovo/h8/acpi/ec.asl

@@ -39,6 +39,10 @@ Device(EC)
 				DKR2, 1,	/* Dock register 2 */
 		Offset (0x2a),
 				EVNT, 8,	/* write will trigger EC event */
+		Offset (0x2f),
+				    , 6,
+				FAND, 1,	/* Fan disengage */
+				FANA, 1,	/* Fan automatic mode enable */
 		Offset (0x30),
 				    , 6,
 				ALMT, 1,	/* Audio Mute + LED */

src/ec/lenovo/h8/acpi/thermal.asl

@@ -11,6 +11,8 @@
  * GNU General Public License for more details.
  */
 
+#include <arch/x86/acpi/statdef.asl>
+
 Scope(\_TZ)
 {
 #if defined (EC_LENOVO_H8_ME_WORKAROUND)
@@ -56,20 +58,30 @@ External (\PPKG, MethodObj)
 			Return (\PPKG ())
 		}
 
-		Method (_CRT, 0, NotSerialized) {
+		/* Get critical temperature in degree celsius */
+		Method (GCRT, 0, NotSerialized) {
 			Store (\TCRT, Local0)
 			if (LGreater (Local0, 0)) {
-				Return (C2K (Local0))
+				Return (Local0)
 			}
-			Return (C2K (127))
+			Return (127)
+		}
+
+		/* Get passive temperature in degree celsius */
+		Method (GPSV, 0, NotSerialized) {
+			Store (\TPSV, Local0)
+			if (LGreater (Local0, 0)) {
+				Return (Local0)
+			}
+			Return (95)
+		}
+
+		Method (_CRT, 0, NotSerialized) {
+			Return (C2K (GCRT ()))
 		}
 
 		Method (_PSV, 0, NotSerialized) {
-			Store (\TPSV, Local0)
+			Return (C2K (GPSV ()))
-			if (LGreater (Local0, 0)) {
-				Return (C2K(Local0))
-			}
-			Return (C2K (95))
 		}
 
 		Method(_TMP) {
@@ -82,6 +94,51 @@ External (\PPKG, MethodObj)
 #endif
 			Return (C2K(\_SB.PCI0.LPCB.EC.TMP0))
 		}
+
+		Method (_AC0) {
+			Store (GPSV (), Local0)
+
+			/* Active fan 10 degree below passive threshold */
+			Subtract (Local0, 10, Local0)
+
+			If (LEqual (\_SB.PCI0.LPCB.EC.FAND, 1)) {
+				/* Turn of 5 degree below trip point */
+				Subtract (Local0, 5, Local0)
+			}
+
+			Return (C2K (Local0))
+		}
+
+		Name (_AL0, Package () { FAN })
+
+		PowerResource (FPwR, 0, 0)
+		{
+			Method (_STA) {
+				If (LEqual (\_SB.PCI0.LPCB.EC.FAND, 0)) {
+					Return (Zero)
+				} Else {
+					Return (One)
+				}
+			}
+
+			Method (_ON) {
+				Store (One, \_SB.PCI0.LPCB.EC.FAND)
+				Store (Zero, \_SB.PCI0.LPCB.EC.FANA)
+				Notify (\_TZ.THM0, NOTIFY_TZ_TRIPPTCHG)
+			}
+
+			Method (_OFF) {
+				Store (Zero, \_SB.PCI0.LPCB.EC.FAND)
+				Store (One, \_SB.PCI0.LPCB.EC.FANA)
+				Notify (\_TZ.THM0, NOTIFY_TZ_TRIPPTCHG)
+			}
+		}
+
+		Device (FAN)
+		{
+			Name (_HID, EISAID ("PNP0C0B"))
+			Name (_PR0, Package () { FPwR })
+		}
 	}
 
 	ThermalZone(THM1)