From 0c3749c41f5eee0da36bbf92b2793338b4d8574f Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 3 Feb 2006 21:51:41 +0100 Subject: [PATCH] x86_64: Calibrate APIC timer using PM timer On some broken motherboards (at least one NForce3 based AMD64 laptop) the PIT timer runs at a incorrect frequency. This patch adds a new option "apicpmtimer" that allows to use the APIC timer and calibrate it using the PMTimer. It requires the earlier patch that allows to run the main timer from the APIC. Specifying apicpmtimer implies apicmaintimer. The option defaults to off for now. I tested it on a few systems and the resulting APIC timer frequencies were usually a bit off, but always <1%, which should be tolerable. TBD figure out heuristic to enable this automatically on the affected systems TBD perhaps do it on all NForce3s or using DMI? Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/apic.c | 33 +++++++++++++++++++++++++++------ arch/x86_64/kernel/pmtimer.c | 20 ++++++++++++++++++++ 2 files changed, 47 insertions(+), 6 deletions(-) (limited to 'arch') diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c index 673a2fe9923c..c02218b3ae2b 100644 --- a/arch/x86_64/kernel/apic.c +++ b/arch/x86_64/kernel/apic.c @@ -40,6 +40,7 @@ int apic_verbosity; int apic_runs_main_timer; +int apic_calibrate_pmtmr __initdata; int disable_apic_timer __initdata; @@ -746,14 +747,27 @@ static int __init calibrate_APIC_clock(void) __setup_APIC_LVTT(1000000000); apic_start = apic_read(APIC_TMCCT); - rdtscl(tsc_start); - - do { +#ifdef CONFIG_X86_PM_TIMER + if (apic_calibrate_pmtmr && pmtmr_ioport) { + pmtimer_wait(5000); /* 5ms wait */ apic = apic_read(APIC_TMCCT); - rdtscl(tsc); - } while ((tsc - tsc_start) < TICK_COUNT && (apic - apic_start) < TICK_COUNT); + result = (apic_start - apic) * 1000L / 5; + } else +#endif + { + rdtscl(tsc_start); + + do { + apic = apic_read(APIC_TMCCT); + rdtscl(tsc); + } while ((tsc - tsc_start) < TICK_COUNT && + (apic - apic_start) < TICK_COUNT); + + result = (apic_start - apic) * 1000L * cpu_khz / + (tsc - tsc_start); + } + printk("result %d\n", result); - result = (apic_start - apic) * 1000L * cpu_khz / (tsc - tsc_start); printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n", result / 1000 / 1000, result / 1000 % 1000); @@ -1115,6 +1129,13 @@ static __init int setup_noapicmaintimer(char *str) } __setup("noapicmaintimer", setup_noapicmaintimer); +static __init int setup_apicpmtimer(char *s) +{ + apic_calibrate_pmtmr = 1; + return setup_apicmaintimer(NULL); +} +__setup("apicpmtimer", setup_apicpmtimer); + /* dummy parsing: see setup.c */ __setup("disableapic", setup_disableapic); diff --git a/arch/x86_64/kernel/pmtimer.c b/arch/x86_64/kernel/pmtimer.c index 8b2655ae4e61..5c51d10408a6 100644 --- a/arch/x86_64/kernel/pmtimer.c +++ b/arch/x86_64/kernel/pmtimer.c @@ -80,6 +80,26 @@ int pmtimer_mark_offset(void) return lost - 1; } +static unsigned pmtimer_wait_tick(void) +{ + u32 a, b; + for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK; + a == b; + b = inl(pmtmr_ioport) & ACPI_PM_MASK) + ; + return b; +} + +/* note: wait time is rounded up to one tick */ +void pmtimer_wait(unsigned us) +{ + u32 a, b; + a = pmtimer_wait_tick(); + do { + b = inl(pmtmr_ioport); + } while (cyc2us(b - a) < us); +} + void pmtimer_resume(void) { last_pmtmr_tick = inl(pmtmr_ioport); -- cgit v1.2.2