ACPI: Add support for runtime config TDP down

The required power MSRs are mirrored in MCHBAR so
it is possible to configure TDP at runtime via ASL.

This adds the required fields and a set of methods to
configure "TDP down" and "TDP nominal".  It explicitly
does not support "TDP up" at the moment.

PSSS: method is added to assist in searching the _PSS
table for the appropriate entry that corresponds to the
desired max non-turbo ratio.

STND: Set TDP Down from Nominal.  This will limit CPU to
the TDP down configuration by sequencing the required
changes in the right order.

STDN: Set TDP Nominal from Down.  This will set the CPU
back to nominal configuration by sequencing the required
changes in the correct (reverse) order.

This does not introduce any functional changes and must
be paired with additional changes to be useful.

The current configured TDP can be checked to see that
the transition to/from a desired level is successful.

> mmio_read8 0xfed15f50
0x00  # TDP-Nominal

> mmio_read8 0xfed15f50
0x01  # TDP-Down

Change-Id: I31a2f30cc9d134cc5eee980ae9288ae45e71c6e6
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/1344
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/northbridge/intel/sandybridge/acpi/hostbridge.asl

@@ -101,8 +101,125 @@ Device (MCHC)
 		TLUD,	 32,
 	}
 
+	Name (CTCN, 0)		/* CTDP Nominal Select */
+	Name (CTCD, 1)		/* CTDP Down Select */
+	Name (CTCU, 2)		/* CTDP Up Select */
+
+	OperationRegion (MCHB, SystemMemory, DEFAULT_MCHBAR, 0x8000)
+	Field (MCHB, DWordAcc, Lock, Preserve)
+	{
+		Offset (0x5930),
+		CTDN, 15,	/* CTDP Nominal PL1 */
+		Offset (0x59a0),
+		PL1V, 15,	/* Power Limit 1 Value */
+		PL1E, 1,	/* Power Limit 1 Enable */
+		PL1C, 1,	/* Power Limit 1 Clamp */
+		PL1T, 7,	/* Power Limit 1 Time */
+		Offset (0x59a4),
+		PL2V, 15,	/* Power Limit 2 Value */
+		PL2E, 1,	/* Power Limit 2 Enable */
+		PL2C, 1,	/* Power Limit 2 Clamp */
+		PL2T, 7,	/* Power Limit 2 Time */
+		Offset (0x5f3c),
+		TARN, 8,	/* CTDP Nominal Turbo Activation Ratio */
+		Offset (0x5f40),
+		CTDD, 15,	/* CTDP Down PL1 */
+		, 1,
+		TARD, 8,	/* CTDP Down Turbo Activation Ratio */
+		Offset (0x5f48),
+		CTDU, 15,	/* CTDP Up PL1 */
+		, 1,
+		TARU, 8,	/* CTDP Up Turbo Activation Ratio */
+		Offset (0x5f50),
+		CTCS, 2,	/* CTDP Select */
+		Offset (0x5f54),
+		TARS, 8,	/* Turbo Activation Ratio Select */
 	}
 
+	/*
+	 * Search CPU0 _PSS looking for control=arg0 and then
+	 * return previous P-state entry number for new _PPC
+	 *
+	 * Format of _PSS:
+	 *   Name (_PSS, Package () {
+	 *     Package (6) { freq, power, tlat, blat, control, status }
+	 *   }
+	 */
+	External (\_PR.CPU0._PSS)
+	Method (PSSS, 1, NotSerialized)
+	{
+		Store (One, Local0) /* Start at P1 */
+		Store (SizeOf (\_PR.CPU0._PSS), Local1)
+
+		While (LLess (Local0, Local1)) {
+			/* Store _PSS entry Control value to Local2 */
+			ShiftRight (DeRefOf (Index (DeRefOf (Index
+			      (\_PR.CPU0._PSS, Local0)), 4)), 8, Local2)
+			If (LEqual (Local2, Arg0)) {
+				Return (Subtract (Local0, 1))
+			}
+			Increment (Local0)
+		}
+
+		Return (0)
+	}
+
+	/* Set TDP Down */
+	Method (STND, 0, Serialized)
+	{
+		Store ("Set TDP Down", Debug)
+
+		If (LEqual (CTCD, CTCS)) {
+			Return (0)
+		}
+
+		/* Set CTC */
+		Store (CTCD, CTCS)
+
+		/* Set TAR */
+		Store (TARD, TARS)
+
+		/* Set PPC limit and notify OS */
+		Store (PSSS (TARD), PPCM)
+		PPCN ()
+
+		/* Set PL2 to 1.25 * PL1 */
+		Divide (Multiply (CTDD, 125), 100, Local0, PL2V)
+
+		/* Set PL1 */
+		Store (CTDD, PL1V)
+
+		Return (1)
+	}
+
+	/* Set TDP Nominal from Down */
+	Method (STDN, 0, Serialized)
+	{
+		Store ("Set TDP Nominal", Debug)
+
+		If (LEqual (CTCN, CTCS)) {
+			Return (0)
+		}
+
+		/* Set PL1 */
+		Store (CTDN, PL1V)
+
+		/* Set PL2 to 1.25 * PL1 */
+		Divide (Multiply (CTDN, 125), 100, Local0, PL2V)
+
+		/* Set PPC limit and notify OS */
+		Store (PSSS (TARN), PPCM)
+		PPCN ()
+
+		/* Set TAR */
+		Store (TARN, TARS)
+
+		/* Set CTC */
+		Store (CTCN, CTCS)
+
+		Return (1)
+	}
+}
 
 // Current Resource Settings
 

src/northbridge/intel/sandybridge/acpi/sandybridge.asl

@@ -19,8 +19,8 @@
  * MA 02110-1301 USA
  */
 
-#include "hostbridge.asl"
 #include "../sandybridge.h"
+#include "hostbridge.asl"
 
 /* PCI Device Resource Consumption */
 Device (PDRC)