[Intel-gfx] [PATCH 2/2] drm/i915/guc: Skip suspend/resume GuC action on platforms w/o GuC submission

[Tomas Janousek]

Don, Chris,

On Fri, Nov 15, 2019 at 05:19:59PM +0000, Chris Wilson wrote:
> Quoting Summers, Stuart (2019-11-15 17:12:58)
> > On Thu, 2019-11-14 at 17:11 -0800, don.hiatt at intel.com wrote:
> > > From: Don Hiatt <don.hiatt at intel.com>
> > > 
> > > On some platforms (e.g. KBL) that do not support GuC submission, but
> > > the user enabled the GuC communication (e.g for HuC authentication)
> > > calling the GuC EXIT_S_STATE action results in lose of ability to
> > > enter RC6. We can remove the GuC suspend/resume entirely as we do
> > > not need to save the GuC submission status.
> > > 
> > > v2: Do not suspend/resume the GuC on platforms that do not support
> > >     Guc Submission.
> > > v3: Fix typo, move suspend logic to remove goto.
> > > v4: Use intel_guc_submission_is_enabled() to check GuC submission
> > >     status.
> > > 
> > > Signed-off-by: Don Hiatt <don.hiatt at intel.com>
> > 
> > Any reason not to just combine both of these into a single patch?
> 
> Also please remember to include the bugzilla link, ask if the reporter
> wants to be credited, and most important of all a Fixes: so we can
> backport it correctly. If there is no singular cause, point at the
> "guc/huc enabling by default" patch.

This comment of mine can help with the Fixes: line:
https://bugs.freedesktop.org/show_bug.cgi?id=111623#c20

> I bisected this to [cc80b2ef24898dc62242e194270200b01ca758d1] drm/i915/guc:
> Change platform default GuC mode -- I've been running with enable_guc=-1. If
> I had been running with enable_guc=3, I guess it would've bisected to
> [a2904ade3dc28cf1a1b7deded41f4369f75e664c] drm/i915/guc: Don't allow GuC
> submission.
>
> Anyway, it seems that on this Kaby Lake system, loading HuC without GuC
> submission leads to the GPU not entering rc6 and thus keeping the package
> out of C-states. Obviously then it doesn't matter what GuC version it is, be
> it 9.39 or 32.0.3 or whatever.

Also, as mentioned in another comment:

Tested-by: Tomas Janousek <tomi at nomi.cz>

(Do note that I'm running a backport to 5.3,
https://bugs.freedesktop.org/attachment.cgi?id=145969, not drm-tip.)

-- 
Tomáš Janoušek, a.k.a. Pivník, a.k.a. Liskni_si, http://work.lisk.in/