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

Maxim
2007-03-28T13:43:46Z

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;