> -----Original Message----- > From: Lespiau, Damien > Sent: Wednesday, May 14, 2014 12:14 PM > To: Mateo Lozano, Oscar > Cc: Mika Kuoppala; intel-gfx@lists.freedesktop.org; b...@bwidawsk.net; > m...@iki.fi; kris...@linux.intel.com > Subject: Re: [Intel-gfx] [PATCH v3 1/2] drm/i915: add render state > initialization > > On Wed, May 14, 2014 at 10:24:53AM +0000, Mateo Lozano, Oscar wrote: > > Hi Mika, > > > > > -----Original Message----- > > > From: Intel-gfx [mailto:intel-gfx-boun...@lists.freedesktop.org] On > > > Behalf Of Mika Kuoppala > > > Sent: Tuesday, May 06, 2014 3:30 PM > > > To: intel-gfx@lists.freedesktop.org > > > Cc: b...@bwidawsk.net; m...@iki.fi; kris...@linux.intel.com > > > Subject: [Intel-gfx] [PATCH v3 1/2] drm/i915: add render state > > > initialization > > > > > > HW guys say that it is not a cool idea to let device go into rc6 > > > without proper 3d pipeline state. > > > > > > For each new uninitialized context, generate a valid null render > > > state to be run on context creation. > > > > In Android, we have been seeing a problem in BDW D0 stepping (C0 is > > fine), in which actual rendering does not happen, even though > > everything seems to be healthy. The only "tell" seems to be that the > > pixel shader invocation count does not go up. I wouldn´t dare say I > > understand why this fixes our problem, but it clearly does, so feel > > free to add: > > > > Tested-by: Oscar Mateo <oscar.ma...@intel.com> > > Stating the obvious here, mainly for my own understanding :) > > FWIW, that looks like the userspace driver you are using actually relying on > the > kernel setting up a golden state and missing "one bit" or one packet. For > instance it could be that it's missing a 3DSTATE_WM_HZ_OP command (that's > the last fix Ken did in the gen8 render copy state). > > Out of sheer luck (or almost :) we happen to have this working. > > So that's another kind of papering over than the one "needed" for rc6. > > It seems to potentially be a useful service the kernel is providing to user > space > apps though, trying to setup a sane state so user space batches don't hang the > GPU if they are missing one command. Of course hangs can still happen if the > batches themselves have bugs. > > How to be sure that's the correct golden state is another interesting question > we need to answer.
Oops, sorry, I forgot a very important detail: the same userspace driver works just fine with a 3.10 kernel. I attribute this to the fact that the 3.10 kernel didn´t do MI_SET_CONTEXT unless you were explicitly creating contexts, but there could be another explanation, of course. _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
