cpu/intel: >= nehalem: add comments to msr finalize's

Improve documentation of lock down MSRs in finalize().
Most of these aren't documented in public MSRs.

Change-Id: I4fc47bb9b71bdd7907aae65fc18b419a17ae8547
Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
Reviewed-on: http://review.coreboot.org/8294
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Peter Stuge <peter@stuge.se>

src/cpu/intel/haswell/finalize.c

@@ -24,6 +24,11 @@
 #include <cpu/x86/msr.h>
 #include "haswell.h"
 
+/* MSR Documentation based on
+ * "Sandy Bridge Processor Family BIOS Writer's Guide (BWG)"
+ * Document Number 504790
+ * Revision 1.6.0, June 2012 */
+
 #if 0
 static void msr_set_bit(unsigned reg, unsigned bit)
 {
@@ -46,6 +51,7 @@ static void msr_set_bit(unsigned reg, unsigned bit)
 void intel_cpu_haswell_finalize_smm(void)
 {
 #if 0
+	/* Lock C-State MSR */
 	msr_set_bit(MSR_PMG_CST_CONFIG_CONTROL, 15);
 
 	/* Lock AES-NI only if supported */
@@ -70,7 +76,10 @@ void intel_cpu_haswell_finalize_smm(void)
 	msr_set_bit(MSR_PP1_POWER_LIMIT, 31);
 #endif
 
+	/* Lock TM interupts - route thermal events to all processors */
 	msr_set_bit(MSR_MISC_PWR_MGMT, 22);
+
+	/* Lock memory configuration to protect SMM */
 	msr_set_bit(MSR_LT_LOCK_MEMORY, 0);
 #endif
 }