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

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Date:	Wed, 28 Mar 2007 20:04:57 +0200
From:	"Michael S. Tsirkin" <mst@....mellanox.co.il>
To:	Maxim <maximlevitsky@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	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,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [3/6] 2.6.21-rc4: known regressions

> 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@...lanox.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@...lanox.co.il>
> Status     : unknown

...

> > > > From: Jeff Chua <jeff.chua.linux@...il.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@...il.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@...il.com>

Maxim, do you plan to send this upstream?

Acked-by: Michael S. Tsirkin <mst@....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
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