Date: Thu, 9 Jan 2014 10:44:27 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r260473 - stable/10/sys/x86/cpufreq Message-ID: <201401091044.s09AiRZ7083490@svn.freebsd.org>
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Author: mav Date: Thu Jan 9 10:44:27 2014 New Revision: 260473 URL: http://svnweb.freebsd.org/changeset/base/260473 Log: 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. Modified: stable/10/sys/x86/cpufreq/est.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/x86/cpufreq/est.c ============================================================================== --- stable/10/sys/x86/cpufreq/est.c Thu Jan 9 10:40:36 2014 (r260472) +++ stable/10/sys/x86/cpufreq/est.c Thu Jan 9 10:44:27 2014 (r260473) @@ -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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