diff options
| -rw-r--r-- | arch/x86/kernel/tsc.c | 235 |
1 files changed, 181 insertions, 54 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 8e786b0..ac79bd1 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -127,75 +127,202 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet) */ unsigned long native_calibrate_tsc(void) { - unsigned long flags; - u64 tsc1, tsc2, tr1, tr2, delta, pm1, pm2, hpet1, hpet2; - int hpet = is_hpet_enabled(); - unsigned int tsc_khz_val = 0; + u64 tsc1, tsc2, tr1, tr2, tsc, delta, pm1, pm2, hpet1, hpet2; + unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX; + unsigned long flags, tscmin, tscmax; + int hpet = is_hpet_enabled(), pitcnt, i; - local_irq_save(flags); - - tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL); - - outb((inb(0x61) & ~0x02) | 0x01, 0x61); - - outb(0xb0, 0x43); - outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); - outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); - tr1 = get_cycles(); - while ((inb(0x61) & 0x20) == 0); - tr2 = get_cycles(); - - tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); - - local_irq_restore(flags); + /* + * Run 5 calibration loops to get the lowest frequency value + * (the best estimate). We use two different calibration modes + * here: + * + * 1) PIT loop. We set the PIT Channel 2 to oneshot mode and + * load a timeout of 50ms. We read the time right after we + * started the timer and wait until the PIT count down reaches + * zero. In each wait loop iteration we read the TSC and check + * the delta to the previous read. We keep track of the min + * and max values of that delta. The delta is mostly defined + * by the IO time of the PIT access, so we can detect when a + * SMI/SMM disturbance happend between the two reads. If the + * maximum time is significantly larger than the minimum time, + * then we discard the result and have another try. + * + * 2) Reference counter. If available we use the HPET or the + * PMTIMER as a reference to check the sanity of that value. + * We use separate TSC readouts and check inside of the + * reference read for a SMI/SMM disturbance. We dicard + * disturbed values here as well. We do that around the PIT + * calibration delay loop as we have to wait for a certain + * amount of time anyway. + */ + for (i = 0; i < 5; i++) { + + tscmin = ULONG_MAX; + tscmax = 0; + pitcnt = 0; + + local_irq_save(flags); + + /* + * Read the start value and the reference count of + * hpet/pmtimer when available: + */ + tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL); + + /* Set the Gate high, disable speaker */ + outb((inb(0x61) & ~0x02) | 0x01, 0x61); + + /* + * Setup CTC channel 2* for mode 0, (interrupt on terminal + * count mode), binary count. Set the latch register to 50ms + * (LSB then MSB) to begin countdown. + * + * Some devices need a delay here. + */ + outb(0xb0, 0x43); + outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); + outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); + + tsc = tr1 = tr2 = get_cycles(); + + while ((inb(0x61) & 0x20) == 0) { + tr2 = get_cycles(); + delta = tr2 - tsc; + tsc = tr2; + if ((unsigned int) delta < tscmin) + tscmin = (unsigned int) delta; + if ((unsigned int) delta > tscmax) + tscmax = (unsigned int) delta; + pitcnt++; + } + + /* + * We waited at least 50ms above. Now read + * pmtimer/hpet reference again + */ + tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); + + local_irq_restore(flags); + + /* + * Sanity checks: + * + * If we were not able to read the PIT more than 5000 + * times, then we have been hit by a massive SMI + * + * If the maximum is 10 times larger than the minimum, + * then we got hit by an SMI as well. + */ + if (pitcnt > 5000 && tscmax < 10 * tscmin) { + + /* Calculate the PIT value */ + delta = tr2 - tr1; + do_div(delta, 50); + + /* We take the smallest value into account */ + tsc_pit_min = min(tsc_pit_min, (unsigned long) delta); + } + + /* hpet or pmtimer available ? */ + if (!hpet && !pm1 && !pm2) + continue; + + /* Check, whether the sampling was disturbed by an SMI */ + if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) + continue; + + tsc2 = (tsc2 - tsc1) * 1000000LL; + + if (hpet) { + if (hpet2 < hpet1) + hpet2 += 0x100000000ULL; + hpet2 -= hpet1; + tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD)); + do_div(tsc1, 1000000); + } else { + if (pm2 < pm1) + pm2 += (u64)ACPI_PM_OVRRUN; + pm2 -= pm1; + tsc1 = pm2 * 1000000000LL; + do_div(tsc1, PMTMR_TICKS_PER_SEC); + } + + do_div(tsc2, tsc1); + tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2); + } /* - * Preset the result with the raw and inaccurate PIT - * calibration value + * Now check the results. */ - delta = (tr2 - tr1); - do_div(delta, 50); - tsc_khz_val = delta; + if (tsc_pit_min == ULONG_MAX) { + /* PIT gave no useful value */ + printk(KERN_WARNING "TSC: PIT calibration failed due to " + "SMI disturbance.\n"); + + /* We don't have an alternative source, disable TSC */ + if (!hpet && !pm1 && !pm2) { + printk("TSC: No reference (HPET/PMTIMER) available\n"); + return 0; + } + + /* The alternative source failed as well, disable TSC */ + if (tsc_ref_min == ULONG_MAX) { + printk(KERN_WARNING "TSC: HPET/PMTIMER calibration " + "failed due to SMI disturbance.\n"); + return 0; + } + + /* Use the alternative source */ + printk(KERN_INFO "TSC: using %s reference calibration\n", + hpet ? "HPET" : "PMTIMER"); + + return tsc_ref_min; + } - /* hpet or pmtimer available ? */ + /* We don't have an alternative source, use the PIT calibration value */ if (!hpet && !pm1 && !pm2) { - printk(KERN_INFO "TSC calibrated against PIT\n"); - goto out; + printk(KERN_INFO "TSC: Using PIT calibration value\n"); + return tsc_pit_min; } - /* Check, whether the sampling was disturbed by an SMI */ - if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) { - printk(KERN_WARNING "TSC calibration disturbed by SMI, " - "using PIT calibration result\n"); - goto out; + /* The alternative source failed, use the PIT calibration value */ + if (tsc_ref_min == ULONG_MAX) { + printk(KERN_WARNING "TSC: HPET/PMTIMER calibration failed due " + "to SMI disturbance. Using PIT calibration\n"); + return tsc_pit_min; } - tsc2 = (tsc2 - tsc1) * 1000000LL; - - if (hpet) { - printk(KERN_INFO "TSC calibrated against HPET\n"); - if (hpet2 < hpet1) - hpet2 += 0x100000000ULL; - hpet2 -= hpet1; - tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD)); - do_div(tsc1, 1000000); - } else { - printk(KERN_INFO "TSC calibrated against PM_TIMER\n"); - if (pm2 < pm1) - pm2 += (u64)ACPI_PM_OVRRUN; - pm2 -= pm1; - tsc1 = pm2 * 1000000000LL; - do_div(tsc1, PMTMR_TICKS_PER_SEC); + /* Check the reference deviation */ + delta = ((u64) tsc_pit_min) * 100; + do_div(delta, tsc_ref_min); + + /* + * If both calibration results are inside a 5% window, the we + * use the lower frequency of those as it is probably the + * closest estimate. + */ + if (delta >= 95 && delta <= 105) { + printk(KERN_INFO "TSC: PIT calibration confirmed by %s.\n", + hpet ? "HPET" : "PMTIMER"); + printk(KERN_INFO "TSC: using %s calibration value\n", + tsc_pit_min <= tsc_ref_min ? "PIT" : + hpet ? "HPET" : "PMTIMER"); + return tsc_pit_min <= tsc_ref_min ? tsc_pit_min : tsc_ref_min; } - do_div(tsc2, tsc1); - tsc_khz_val = tsc2; + printk(KERN_WARNING "TSC: PIT calibration deviates from %s: %lu %lu.\n", + hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min); -out: - return tsc_khz_val; + /* + * The calibration values differ too much. In doubt, we use + * the PIT value as we know that there are PMTIMERs around + * running at double speed. + */ + printk(KERN_INFO "TSC: Using PIT calibration value\n"); + return tsc_pit_min; } - #ifdef CONFIG_X86_32 /* Only called from the Powernow K7 cpu freq driver */ int recalibrate_cpu_khz(void) |
