linux-kernel - Re: [PATCH v2] Add suspend/resume for HPET

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Message-Id: <1175356272.28263.27.camel@localhost.localdomain>
Date:	Sat, 31 Mar 2007 17:51:11 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Jeff Chua <jeff.chua.linux@...il.com>,
	Adrian Bunk <bunk@...sta.de>,
	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>
Subject: Re: [PATCH v2] Add suspend/resume for HPET

On Thu, 2007-03-29 at 15:46 +0200, Maxim Levitsky wrote:
> Subject: Add suspend/resume for HPET
> This adds support of suspend/resume on i386 for HPET
> Signed-off-by: Maxim Levitsky <maximlevitsky@...il.com>
>
> +static struct sysdev_class hpet_class = {
> +	set_kset_name("hpet"),
> +	.suspend	= hpet_suspend,
> +	.resume		= hpet_resume,
> +};
> +
> +static struct sys_device hpet_device = {
> +	.id		= 0,
> +	.cls		= &hpet_class,
> +};

Sorry for being inresponsive. I was travelling and unexpectedly cut off
from the internet for some days.

While I agree in principle with the patch, I'm a bit uncomfortable. The
sys device suspend / resume ordering is not guaranteed and relies on the
registering order.

Jeff still seems to have problems with CONFIG_NO_HZ=n and it might be
caused by time keeping / tick management resume happening before the
HPET resume.

The required resume order is:

clocksources
timekeeping
clockevents
tick management

I'm not sure how to do this properly with the sys device facilities, but
I look into it.

/me goes off to understand the sys device magic.

	tglx


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