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

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( 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 code unconditionally enables timed MWAIT, but not all Haswell
steppings support it. In preparation for merging Haswell and Broadwell,
also enable timed MWAIT on Haswell code, but only if it is supported.

Change-Id: I1d11d62f1801d65ae4d5623994fd55fd35e8f34a
Signed-off-by: Angel Pons 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46916
Reviewed-by: Arthur Heymans 
Tested-by: build bot (Jenkins) 
---
M src/cpu/intel/haswell/haswell.h
M src/cpu/intel/haswell/haswell_init.c
2 files changed, 8 insertions(+), 1 deletion(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved

diff --git a/src/cpu/intel/haswell/haswell.h b/src/cpu/intel/haswell/haswell.h
index 87c4e0a..cb602ce 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 0e48876..9881bb8 100644
--- a/src/cpu/intel/haswell/haswell_init.c
+++ b/src/cpu/intel/haswell/haswell_init.c
@@ -431,7 +431,9 @@

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
@@ -441,6 +443,10 @@
    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);