Re: [3/6] 2.6.21-rc4: known regressions

Randy Dunlap
2007-03-28T18:35:55Z

On Wed, 28 Mar 2007 20:04:57 +0200 Michael S. Tsirkin wrote:

> > Subject : first disk access after resume takes several minutes
> > ('date' does not advance after resume from RAM, CONFIG_NO_HZ=n)
> > References : http://lkml.org/lkml/2007/3/8/117
> > http://lkml.org/lkml/2007/3/25/20
> > Submitter : Michael S. Tsirkin <mst@mellanox.co.il>
>
> ...
>
> > Subject : after resume: X hangs after drawing a couple of windows
> > References : http://lkml.org/lkml/2007/3/8/117
> > Submitter : Michael S. Tsirkin <mst@mellanox.co.il>
> > Status : unknown
>
> ...
>
> > > > > From: Jeff Chua <jeff.chua.linux@gmail.com>
> > > > > > 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.
> >
> > Quoting Maxim <maximlevitsky@gmail.com>:
> >
> > 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
>
> Bingo!
>
> The patch below fixes the two problems (listed above) with
> resume from RAM that I have observed on my T60 with
> 2.6.21-rc5: with this patch applied, and with CONFIG_NO_HZ
> unset, date advances correctly, X functions properly and
> there is no delay on first disk access.
>
> Thanks very much.
>
> ---
> > Add suspend/resume for HPET
> > Signed-off-by: Maxim Levitsky <maximlevisky@gmail.com>
>
> Maxim, do you plan to send this upstream?

with whitespace fixes, please...

> Acked-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
>
> ---
>
> 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)
> + {

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);
> +

delete above line.

> + }
> +
> +
> switch(mode) {
> case CLOCK_EVT_MODE_PERIODIC:
> delta = ((uint64_t)(NSEC_PER_SEC/HZ)) * hpet_clockevent.mult;

---
~Randy
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