svn commit: r260602 - stable/8/sys/x86/cpufreq

Alexander Motin mav at
Mon Jan 13 19:14:30 UTC 2014

Author: mav
Date: Mon Jan 13 19:14:29 2014
New Revision: 260602

  MFC r259197:
  Do not DELAY() for P-state transition unless we want to see the result.
  Intel manual says: "If a transition is already in progress, transition to
  a new value will subsequently take effect. Reads of IA32_PERF_CTL determine
  the last targeted operating point."  So seems it should be fine to just
  trigger wanted transition and go.  Linux does the same.

Directory Properties:
  stable/8/   (props changed)
  stable/8/sys/   (props changed)
  stable/8/sys/x86/   (props changed)

Modified: stable/8/sys/x86/cpufreq/est.c
--- stable/8/sys/x86/cpufreq/est.c	Mon Jan 13 19:08:25 2014	(r260601)
+++ stable/8/sys/x86/cpufreq/est.c	Mon Jan 13 19:14:29 2014	(r260602)
@@ -1288,10 +1288,9 @@ est_set_id16(device_t dev, uint16_t id16
 	msr = (msr & ~0xffff) | id16;
 	wrmsr(MSR_PERF_CTL, msr);
-	/* Wait a short while for the new setting.  XXX Is this necessary? */
 	if  (need_check) {
+		/* Wait a short while and read the new status. */
 		if (new_id16 != id16) {
 			if (bootverbose)

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