Date: Sun, 16 Dec 2012 11:16:14 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: svn commit: r244287 - projects/calloutng/sys/x86/isa Message-ID: <201212161116.qBGBGEwn063983@svn.freebsd.org>
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Author: mav Date: Sun Dec 16 11:16:13 2012 New Revision: 244287 URL: http://svnweb.freebsd.org/changeset/base/244287 Log: Mostly out of fun, teach i8254 eventtimer driver to program only LSB for very short time intervals (<214us). This allows to get less then 22us usleep(1) time from this anscient timer. It is even better then HPET time now, just with much higher CPU usage. Modified: projects/calloutng/sys/x86/isa/clock.c Modified: projects/calloutng/sys/x86/isa/clock.c ============================================================================== --- projects/calloutng/sys/x86/isa/clock.c Sun Dec 16 10:12:40 2012 (r244286) +++ projects/calloutng/sys/x86/isa/clock.c Sun Dec 16 11:16:13 2012 (r244287) @@ -125,6 +125,7 @@ struct attimer_softc { static struct attimer_softc *attimer_sc = NULL; static int timer0_period = -2; +static int timer0_last = 0xffff; /* Values for timerX_state: */ #define RELEASED 0 @@ -433,11 +434,17 @@ set_i8254_freq(int mode, uint32_t period outb(TIMER_CNTR0, new_count >> 8); break; case MODE_ONESHOT: + if (new_count < 256 && timer0_last < 256) { + outb(TIMER_MODE, TIMER_SEL0 | TIMER_INTTC | TIMER_LSB); + outb(TIMER_CNTR0, new_count & 0xff); + break; + } outb(TIMER_MODE, TIMER_SEL0 | TIMER_INTTC | TIMER_16BIT); outb(TIMER_CNTR0, new_count & 0xff); outb(TIMER_CNTR0, new_count >> 8); break; } + timer0_last = new_count; out: mtx_unlock_spin(&clock_lock); }
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