linux-kernel - Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems

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Message-ID: <20170523130616.GC25383@nazgul.tnic>
Date:   Tue, 23 May 2017 15:06:16 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Ghannam, Yazen" <Yazen.Ghannam@....com>
Cc:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "len.brown@...el.com" <len.brown@...el.com>,
        "pavel@....cz" <pavel@....cz>
Subject: Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD
 systems

On Tue, May 23, 2017 at 12:50:15PM +0000, Ghannam, Yazen wrote:
> No, AMD systems will continue to use HLT unless the BIOS specifies the
> use of MWAIT using a FFH entry in the ACPI _CST.
> 
> All this change does is *allow* us to use MWAIT through the FFH
> implementation if the BIOS defines it. It doesn't *force* a change.

So that could very well be part of the commit message as it explains
what exactly you're changing.

> If the BIOS doesn't define the appropriate _CST entry or it defines it
> wrong, then we'll fallback to using HLT.

I'm assuming you've tested it on older families to make sure they still
work as expected? I wouldn't trust the BIOS...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--