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    SubjectRe: [3/6] 2.6.21-rc4: known regressions
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    On Wednesday 28 March 2007 09:04:28 Thomas Gleixner wrote:
    > On Tue, 2007-03-27 at 01:46 +0800, Jeff Chua wrote:
    > > On 3/27/07, Thomas Gleixner <tglx@linutronix.de> wrote:
    > >
    > > > > It's related. I tested without CONFIG_HPET_TIMER, and now my X60 can
    > > > > suspend and resume from RAM (s2ram). Even better, it works
    > > > > with/without CONFIG_NO_HZ.
    > > >
    > > > Does the patch below fix the HPET_TIMER=y case ?
    > >
    > > Thomas, I tried, but it didn't help. Upon resume from ram, "date"
    > > still didn't advance.
    >
    > Can you please issue a SysRq-Q in this situation and provide the dmesg
    > output ?
    >
    > Thanks,
    >
    > tglx
    >
    >
    > -
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    >

    Hi,
    I almost sure Iknow why this happens,
    The problem is that both hpet clock source and hpet clockevents doesn't have a suspend/resume function
    On resume we should enable the main counter _and_ enable legacy replacement mode,
    On my system main counter in enabled, by I think by bios, but legacy replacement mode is not, so if
    a system doesn't use lapic as a tick source, but use hpet+broadcast, it will hang for sure on resume, and i tested it

    The patch below is a temporally fix, until clock-events and clocksources will get proper suspend/resume hooks:

    Regards,
    Maxim Levitsky

    ---

    Add suspend/resume for HPET
    Signed-off-by: Maxim Levitsky <maximlevisky@gmail.com>

    ---

    diff --git a/arch/i386/kernel/hpet.c b/arch/i386/kernel/hpet.c
    index 0fd9fba..a1ec79e 100644
    --- a/arch/i386/kernel/hpet.c
    +++ b/arch/i386/kernel/hpet.c
    @@ -152,6 +152,16 @@ static void hpet_set_mode(enum clock_event_mode mode,
    unsigned long cfg, cmp, now;
    uint64_t delta;

    +
    + if ( mode != CLOCK_EVT_MODE_UNUSED && mode != CLOCK_EVT_MODE_SHUTDOWN)
    + {
    + unsigned long cfg = hpet_readl(HPET_CFG);
    + cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
    + hpet_writel(cfg, HPET_CFG);
    +
    + }
    +
    +
    switch(mode) {
    case CLOCK_EVT_MODE_PERIODIC:
    delta = ((uint64_t)(NSEC_PER_SEC/HZ)) * hpet_clockevent.mult;
    -
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