[coreboot-gerrit] Change in coreboot[master]: cpu/intel/haswell: Enable timed MWAIT if supported

[Angel Pons (Code Review)]

Angel Pons has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/46916 )

Change subject: cpu/intel/haswell: Enable timed MWAIT if supported
......................................................................

cpu/intel/haswell: Enable timed MWAIT if supported

Broadwell unconditionally enables it, but not all Haswell steppings
support it. Thus, check the capability bit before attempting to set it.

Change-Id: I1d11d62f1801d65ae4d5623994fd55fd35e8f34a
Signed-off-by: Angel Pons 
---
M src/cpu/intel/haswell/haswell.h
M src/cpu/intel/haswell/haswell_init.c
2 files changed, 8 insertions(+), 1 deletion(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/16/46916/1

diff --git a/src/cpu/intel/haswell/haswell.h b/src/cpu/intel/haswell/haswell.h
index b23fbac..2352489 100644
--- a/src/cpu/intel/haswell/haswell.h
+++ b/src/cpu/intel/haswell/haswell.h
@@ -36,6 +36,7 @@
 #define MSR_CORE_THREAD_COUNT		0x35
 #define MSR_PLATFORM_INFO		0xce
 #define  PLATFORM_INFO_SET_TDP		(1 << 29)
+#define  TIMED_MWAIT_SUPPORTED		(1 << (37 - 32))
 #define MSR_PKG_CST_CONFIG_CONTROL	0xe2
 #define MSR_PMG_IO_CAPTURE_BASE		0xe4
 #define MSR_FEATURE_CONFIG		0x13c
diff --git a/src/cpu/intel/haswell/haswell_init.c b/src/cpu/intel/haswell/haswell_init.c
index 438a317..21f3f4a 100644
--- a/src/cpu/intel/haswell/haswell_init.c
+++ b/src/cpu/intel/haswell/haswell_init.c
@@ -433,7 +433,9 @@

static void configure_c_states(void)
 {
-	msr_t msr;
+	msr_t msr = rdmsr(MSR_PLATFORM_INFO);
+
+	const bool timed_mwait_capable = !!(msr.hi & TIMED_MWAIT_SUPPORTED);

msr = rdmsr(MSR_PKG_CST_CONFIG_CONTROL);
    msr.lo |= (1 << 30);	// Package c-state Undemotion Enable
@@ -443,6 +445,10 @@
    msr.lo |= (1 << 26);	// C1 Auto Demotion Enable
    msr.lo |= (1 << 25);	// C3 Auto Demotion Enable
    msr.lo &= ~(1 << 10);	// Disable IO MWAIT redirection
+
+	if (timed_mwait_capable)
+		msr.lo |= (1 << 31);	// Timed MWAIT Enable
+
    /* The deepest package c-state defaults to factory-configured value. */
    wrmsr(MSR_PKG_CST_CONFIG_CONTROL, msr);