[Intel-gfx] [PATCH] drm/i915: Allow set context SSEU on platforms after gen 11

[Chris Wilson]

Quoting Summers, Stuart (2019-09-20 22:09:46)
> On Thu, 2019-09-19 at 08:00 +0100, Tvrtko Ursulin wrote:
> > On 18/09/2019 18:31, Stuart Summers wrote:
> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110559
> > 
> > Unless there was some discussion I missed we can't just turn it on
> > to 
> > work around a SKIP in IGT. Feature was deliberately limited to
> > Icelake 
> > and even there just to a sub-set of possible configurations.
> 
> No conversation was missed, or at least none I was a part of. Is there
> a reason we don't allow this on future platforms?
> 
> We do claim powergate support on TGL, so I assumed it would be good to
> take this path on that platform. Maybe I'm misunderstanding something
> here though.

The current interface is purely to work around a silicon issue on icl.
It was not developed into a fully reconfigurable sseu interface mostly
due to a lack of demonstrable need and a lack of appreciation of the
tradeoffs between different system users (along with the claim that this
is all meant to be handled by instructions in the command stream...).
Another team did try to autoadjust sseu but also did not produce the
rationale nor attempt to integrate with the existing code.
-Chris