linux-kernel - Re: [PATCH] ACPI/NVS: Not save NVS region for new machines to accelerate S3

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Message-ID: <20140721050105.GA21503@gchen.bj.intel.com>
Date:	Mon, 21 Jul 2014 01:01:05 -0400
From:	"Chen, Gong" <gong.chen@...ux.intel.com>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	rjw@...ysocki.net, lenb@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI/NVS: Not save NVS region for new machines to
 accelerate S3

On Mon, Jul 21, 2014 at 10:14:31AM +0800, Lan Tianyu wrote:
> Date: Mon, 21 Jul 2014 10:14:31 +0800
> From: Lan Tianyu <tianyu.lan@...el.com>
> To: rjw@...ysocki.net, lenb@...nel.org, linux-acpi@...r.kernel.org,
>  linux-kernel@...r.kernel.org, gong.chen@...ux.intel.com
> Subject: Re: [PATCH] ACPI/NVS: Not save NVS region for new machines to
>  accelerate S3
> User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:14.0) Gecko/20120714
>  Thunderbird/14.0
> 
> On 2014年07月18日 16:00, Chen, Gong wrote:
> > On Fri, Jul 18, 2014 at 01:55:22PM +0800, Lan Tianyu wrote:
> >> Date:	Fri, 18 Jul 2014 13:55:22 +0800
> >> From: Lan Tianyu <tianyu.lan@...el.com>
> >> To: rjw@...ysocki.net, lenb@...nel.org
> >> Cc: Lan Tianyu <tianyu.lan@...el.com>, linux-acpi@...r.kernel.org,
> >>  linux-kernel@...r.kernel.org
> >> Subject: [PATCH] ACPI/NVS: Not save NVS region for new machines to
> >>  accelerate S3
> >> X-Mailer: git-send-email 1.7.9.5
> >>
> >> NVS region is saved and restored unconditionally for machines without
> >> nvs_nosave quirk during S3. Tested some new machines and the operation
> >> is not necessary. Saving NVS region also affects S2RAM speed. The time of
> >> NVS saving and restoring depends on the size of NVS region and it consumes
> >> 7~10ms normally.
> >>
> >> This patch is to make machines produced from 2012 to now not saving NVS region
> >> to accelerate S3.
> >>
> > The year 2012 is a mandatory value in the spec?
> > 
> 
> No, spec indicates that this is only required for S4 and commit 2a6b697
> added this behavior because this can fix S3 bug on some machines. But
> this isn't necessary for all machines and waster time for S3. So this
> patch is to add time base quirk to change default behavior for new machines.
> 
If so, I don't think a hard-coded valud in the kernel is a good idea.
Why not providing a quirk via a command line parameter or module parameter.

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