google/panther: Re-read temperature if current reading would cause power-off

Sometimes the SuperIO seems to provide wrong readings, especially early
on after a resume from suspend. This will cause the system to power off.
If that happens, wait for 1s and read again, to make sure the high
temperature value was not just a flaky read.

BUG=chrome-os-partner:24918
BRANCH=panther
TEST=Boot tested on Panther.

Change-Id: Ib3768528d90e34448e96ad587b2503d8d8b1a775
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Signed-off-by: Stefan Reinauer <reinauer@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/182188
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Tested-by: Stefan Reinauer <reinauer@chromium.org>
Commit-Queue: Stefan Reinauer <reinauer@chromium.org>
Reviewed-on: http://review.coreboot.org/6001
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/mainboard/google/panther/acpi/thermal.asl

@@ -61,7 +61,7 @@ Scope (\_TZ)
 			Return (\PPKG ())
 		}
 
-		Method (_TMP, 0, Serialized)
+		Method (TCHK, 0, Serialized)
 		{
 			// Get CPU Temperature from PECI via SuperIO TMPIN3
 			Store (\_SB.PCI0.LPCB.SIO.ENVC.TIN3, Local0)
@@ -84,6 +84,31 @@ Scope (\_TZ)
 			Return (CTOK (Local0))
 		}
 
+		Method (_TMP, 0, Serialized)
+		{
+			// Get temperature from SuperIO in deci-kelvin
+			Store (TCHK (), Local0)
+
+			// Critical temperature in deci-kelvin
+			Store (CTOK (\TMAX), Local1)
+
+			If (LGreaterEqual (Local0, Local1)) {
+				Store ("CRITICAL TEMPERATURE", Debug)
+				Store (Local0, Debug)
+
+				// Wait 1 second for SuperIO to re-poll
+				Sleep (1000)
+
+				// Re-read temperature from SuperIO
+				Store (TCHK (), Local0)
+
+				Store ("RE-READ TEMPERATURE", Debug)
+				Store (Local0, Debug)
+			}
+
+			Return (Local0)
+		}
+
 		Method (_AC0) {
 			If (LLessEqual (\FLVL, 0)) {
 				Return (CTOK (\F0OF))