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

Michael S. Tsirkin
2007-03-28T18:04:21Z

> 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?

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)
+ {
+ 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;

--
MST