[Intel-gfx] [PATCH 51/53] drm/i915/bdw: Document Logical Rings, LR contexts and Execlists

[Mateo Lozano, Oscar]

> -----Original Message-----
> From: daniel.vetter at ffwll.ch [mailto:daniel.vetter at ffwll.ch] On Behalf Of
> Daniel Vetter
> Sent: Tuesday, June 17, 2014 11:09 AM
> To: Mateo Lozano, Oscar
> Cc: Chris Wilson; intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH 51/53] drm/i915/bdw: Document Logical
> Rings, LR contexts and Execlists
> 
> On Tue, Jun 17, 2014 at 11:46 AM, Mateo Lozano, Oscar
> <oscar.mateo at intel.com> wrote:
> > The comment appears in the commit message for " drm/i915/bdw:
> Implement context switching (somewhat) ":
> >
> >     v3: Use LRCA[31:12] as hwCtxId[19:0]. This guarantees that the HW
> context
> >     ID we submit to the ELSP is globally unique and != 0 (Bspec requirements
> >     of the software use-only bits of the Context ID in the Context Descriptor
> >     Format) without the hassle of the previous submission Id construction.
> 
> I've meant a comment as to why reusing ctx->id isn't a good idea since it's
> per-file an so not globally unique. Occasionally repeating and stating the
> seemingly obvious won't hurt ;-) -Daniel

Ok, I´ll expand the comment describing why the submission Id construction was a very bad idea.