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    SubjectRe: PMTMR running too fast
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    On Mon, 2006-12-04 at 19:40 +0000, Ian Campbell wrote:
    > On Mon, 2006-12-04 at 11:19 -0800, john stultz wrote:
    > > On Sun, 2006-12-03 at 13:50 +0000, Ian Campbell wrote:
    > > > In older kernels arch/i386/kernel/timers/timer_pm.c:verify_pmtmr_rate
    > > > contained a check for sensible PMTMR rate and disabled that clocksource
    > > > if it was found to be out of spec[0]. This check seems to have been lost
    > > > in the transition to drivers/clocksource/acpi_pm.c, the removal is in
    > > > 61743fe445213b87fb55a389c8d073785323ca3e "Time: i386 Conversion - part
    > > > 4: Remove Old timer_opts Code"[1] and the check is not present in the
    > > > replacement 5d0cf410e94b1f1ff852c3f210d22cc6c5a27ffa "Time: i386
    > > > Clocksource Drivers"[2].
    > >
    > > Fedora has a bug covering this:
    > > https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=211902
    >
    > > > Is there a specific reason the check was removed (I couldn't see on in
    > > > the archives) or was it simply overlooked? Without it I need to pass
    > > > clocksource=tsc to have 2.6.18 work correctly on an older K6 system with
    > > > an Aladdin chipset (will dig out the precise details if required). Would
    > > > a patch to reintroduce the check be acceptable or would some sort of
    > > > blacklist based solution be more acceptable?
    > >
    > > If I recall correctly, it was pulled because there was some question as
    > > to if it was actually needed (x86_64 didn't need it) and it slows down
    > > the boot time (although not by much).
    > >
    > > I'm fine just re-adding it. Although if the number of affected systems
    > > are small we could just blacklist it (Ian, mind sending dmidecode
    > > output?).

    I don't have a dev box to test on at the moment, but here's a quick hack
    attempt at re-adding the code. Does the following work for you?

    thanks
    -john


    diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
    index 7fcb77a..3379b5f 100644
    --- a/drivers/clocksource/acpi_pm.c
    +++ b/drivers/clocksource/acpi_pm.c
    @@ -21,9 +21,12 @@ #include <linux/errno.h>
    #include <linux/init.h>
    #include <linux/pci.h>
    #include <asm/io.h>
    +#include "mach_timer.h"

    /* Number of PMTMR ticks expected during calibration run */
    #define PMTMR_TICKS_PER_SEC 3579545
    +#define PMTMR_EXPECTED_RATE \
    + ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))

    /*
    * The I/O port the PMTMR resides at.
    @@ -142,6 +145,36 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SE
    acpi_pm_check_graylist);
    #endif

    +#ifndef CONFIG_X86_64
    +/*
    + * 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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