From: tb <tb@openbsd.org>
Date: Wed, 11 Aug 2021 18:31:48 +0000 (+0000)
Subject: Do not read the status MSR before setting performance adjustment mode.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=04a8cccc8570b51bcf508309bfd188a2c7f8a197;p=openbsd

Do not read the status MSR before setting performance adjustment mode.
This makes modifying hw.setperf and apmd -A work on robert's laptop.
Previously, it would sometimes be impossible to set hw.setperf to any
value on this machine.

Keep a delay loop that waits for the MSR write to take effect before
setting hw.cpuspeed to the new value since this is apparently needed
for some pre-ryzen processors.

Debugging, initial diff & test by robert

ok brynet
---

diff --git a/sys/arch/amd64/amd64/k1x-pstate.c b/sys/arch/amd64/amd64/k1x-pstate.c
index cb79e0cc6a8..8245c00518a 100644
--- a/sys/arch/amd64/amd64/k1x-pstate.c
+++ b/sys/arch/amd64/amd64/k1x-pstate.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: k1x-pstate.c,v 1.10 2017/12/27 17:41:54 fcambus Exp $ */
+/*	$OpenBSD: k1x-pstate.c,v 1.11 2021/08/11 18:31:48 tb Exp $ */
 /*
  * Copyright (c) 2011 Bryan Steele <brynet@gmail.com>
  *
@@ -97,21 +97,13 @@ k1x_transition(struct k1x_cpu_state *cstate, int level)
 	u_int64_t msr;
 	int i, cfid, fid = cstate->state_table[level].fid;
 
-	msr = rdmsr(MSR_K1X_STATUS);
-	cfid = K1X_FID(msr);
-
-	if (fid == cfid)
-		return;
-
-	if (cfid != fid) {
-		wrmsr(MSR_K1X_CONTROL, fid);
-		for (i = 0; i < 100; i++) {
-			msr = rdmsr(MSR_K1X_STATUS);
-			if (K1X_FID(msr) == fid)
-				break;
-			DELAY(100);
-		}
+	wrmsr(MSR_K1X_CONTROL, fid);
+	for (i = 0; i < 100; i++) {
+		msr = rdmsr(MSR_K1X_STATUS);
 		cfid = K1X_FID(msr);
+		if (cfid == fid)
+			break;
+		DELAY(100);
 	}
 	if (cfid == fid) {
 		cpuspeed = cstate->state_table[level].freq;