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

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Message-ID: <20140721062556.GA23297@gchen.bj.intel.com>
Date:	Mon, 21 Jul 2014 02:25:56 -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 01:54:56PM +0800, Lan Tianyu wrote:
> Date: Mon, 21 Jul 2014 13:54:56 +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21日 13:01, Chen, Gong wrote:
> > 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.
> > 
> 
> There is already a kernel command "acpi_sleep=nonvs_s3" to do that. But
> this needs to be set by user. Otherwise, saving/restoring NVS region
> also breaks system suspend on some machines and we have added 14
> nonvs quirks in the acpisleep_dmi_table.
> 
14 quriks! What a terrible BIOS, isn't it? It's time to cleanup so
many hacks. I'm not ACPI expert, but such yet another hack is not
acceptable from my point of view.

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