linux-kernel - Re: [PATCH] drm/i915: fix long-standing SNB regression in power consumption after resume

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Message-ID: <20130716083140.GK2823@cantiga.alporthouse.com>
Date:	Tue, 16 Jul 2013 09:31:40 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	David Airlie <airlied@...ux.ie>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/i915: fix long-standing SNB regression in power
 consumption after resume

On Tue, Jul 16, 2013 at 09:44:59AM +0200, Daniel Vetter wrote:
> The issue I have with the current patch is that it looks a bit like
> duct-tape since the point where we drop the forcewake references seems to
> lack justification. The write to MBCTL itself will temporarily wake up the
> chip, so just wrapping that up in with forcewake is very likely not good
> enough. So I fear that we'll only hold forcewake long enough on most
> systems and still have a bunch of oddball broken systems out there.
> 
> Holding forcewake otoh until we've fully set up rps/rc6 makes imo tons of
> sense, hence why I've brought up the idea. Same reasoning applies to
> extending the w/a to all systems supporting rc6.

In which case disable rc6 at the start of init gating and only enable it
at the end of the deferred task. That I think will better test your
hypothesis and make the transistion steps clearer.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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