Re: vlv punit and sideband tidy

From: Chris Wilson <chris@chris-wilson.co.uk>
To: "Rogozhkin, Dmitry V" <dmitry.v.rogozhkin@intel.com>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>
Subject: Re: vlv punit and sideband tidy
Date: Thu, 08 Mar 2018 16:49:21 +0000	[thread overview]
Message-ID: <152052776144.18139.18267350248752892403@mail.alporthouse.com> (raw)
In-Reply-To: <1520426192.13504.1.camel@intel.com>

Quoting Rogozhkin, Dmitry V (2018-03-07 20:39:16)
> On Wed, 2018-03-07 at 19:41 +0000, Chris Wilson wrote:
> > Mika
> > believes that if we keep the cpu in C0 whilst the gpu is busy, then
> > it
> > behaves much better -- but that is a very tough sell
> 
> Chris, Mika, I wonder does i915 driver tries to keep CPU in C0 at the
> moment already or you just consider this? 

That is what Mika looked at, setting C0 while the GPU is marked busy.
Iirc, he was satisfied with the result, I just objected on the grounds
that keeping the CPU at max frequency was unlikely to win any friends in
HTPC. (Although, maybe my gut feeling here is backwards and killawatt
reports differently.)

> CPU while gpu is busy, could you, please, clarify what exactly and
> point me to the code/key patches? Please, answer from BDW/SKL gen
> perspective rather than VLV.

Basically you do pm_qos_update_request() from i915_request::mark_busy().
-Chris
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