Author: mav
Date: Tue Dec 10 20:25:43 2013
New Revision: 259197
URL: http://svnweb.freebsd.org/changeset/base/259197
Log:
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.
MFC after: 1 month
Modified:
head/sys/x86/cpufreq/est.c
Modified: head/sys/x86/cpufreq/est.c
==============================================================================
--- head/sys/x86/cpufreq/est.c Tue Dec 10 20:09:49 2013 (r259196)
+++ head/sys/x86/cpufreq/est.c Tue Dec 10 20:25:43 2013 (r259197)
@@ -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? */
- DELAY(EST_TRANS_LAT);
-
if (need_check) {
+ /* Wait a short while and read the new status. */
+ DELAY(EST_TRANS_LAT);
est_get_id16(&new_id16);
if (new_id16 != id16) {
if (bootverbose)
_______________________________________________
svn-src-head@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
