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

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Date:	Wed, 28 Mar 2007 15:43:46 +0200
From:	Maxim <maximlevitsky@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Jeff Chua <jeff.chua.linux@...il.com>,
	Adrian Bunk <bunk@...sta.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, pavel@...e.cz,
	linux-pm@...ts.osdl.org, gregkh@...e.de,
	linux-pci@...ey.karlin.mff.cuni.cz,
	Jens Axboe <jens.axboe@...cle.com>,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
	jgarzik@...ox.com, linux-ide@...r.kernel.org,
	"Michael S. Tsirkin" <mst@...lanox.co.il>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [3/6] 2.6.21-rc4: known regressions

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@...utronix.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@...il.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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