Date: Tue, 10 Dec 2013 20:25:44 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r259197 - head/sys/x86/cpufreq Message-ID: <201312102025.rBAKPiNh005301@svn.freebsd.org>
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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)
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