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    Subject[PATCH -mm] [Time] Re-add verify_pmtmr_rate
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    Date
    Andrew,
    This should go for a round or two in -mm but should be good for
    inclusion into 2.6.20.

    This patch re-adds the verify_pmtmr_rate functionality from 2.6.17 that
    I dropped 2.6.18.

    This resolves problems seen on older K6 ASUS boards where the ACPI PM
    timer runs too fast.

    See:
    https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=211902
    http://bugme.osdl.org/show_bug.cgi?id=2375

    Thanks to Ian Campbell for re-reporting this and testing the fix!

    Signed-off-by: John Stultz <johnstul@us.ibm.com>

    ---
    diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
    index 7fcb77a..8ab61ef 100644
    --- a/drivers/clocksource/acpi_pm.c
    +++ b/drivers/clocksource/acpi_pm.c
    @@ -142,6 +142,39 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SE
    acpi_pm_check_graylist);
    #endif

    +#ifndef CONFIG_X86_64
    +#include "mach_timer.h"
    +#define PMTMR_EXPECTED_RATE \
    + ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
    +/*
    + * Some boards have the PMTMR running way too fast. We check
    + * the PMTMR rate against PIT channel 2 to catch these cases.
    + */
    +static int verify_pmtmr_rate(void)
    +{
    + u32 value1, value2;
    + unsigned long count, delta;
    +
    + mach_prepare_counter();
    + value1 = read_pmtmr();
    + mach_countup(&count);
    + value2 = read_pmtmr();
    + delta = (value2 - value1) & ACPI_PM_MASK;
    +
    + /* Check that the PMTMR delta is within 5% of what we expect */
    + if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
    + delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
    + printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% "
    + "of normal - aborting.\n",
    + 100UL * delta / PMTMR_EXPECTED_RATE);
    + return -1;
    + }
    +
    + return 0;
    +}
    +#else
    +#define verify_pmtmr_rate() (0)
    +#endif

    static int __init init_acpi_pm_clocksource(void)
    {
    @@ -173,6 +206,9 @@ static int __init init_acpi_pm_clocksour
    return -ENODEV;

    pm_good:
    + if (verify_pmtmr_rate() != 0)
    + return -ENODEV;
    +
    return clocksource_register(&clocksource_acpi_pm);
    }


    -
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