On 01/24/12 18:55, Eric Anholt wrote: > On Sat, 21 Jan 2012 17:36:13 +0100, Daniel Vetter<daniel at ffwll.ch> wrote: >> On Thu, Jan 19, 2012 at 10:50:06AM -0800, Eric Anholt wrote: >>> Older specs claimed this was bit 11, but newer specs and the actual >>> simulator code say it was bit 12. Regardless, we don't use MI_FLUSH, >>> or try to enable it any more. >>> >>> Signed-off-by: Eric Anholt<eric at anholt.net> >> >> I'd like to amend this with the following (on this patch instead of the >> other, so that ppl actually can find it with git blame): >> >> "Furthermore actually setting bit12 results in gpu hangs both on snb and >> ivb. Ben Widawsky discovered a ppt that claims that both bit12 and bit11 >> must be set, but that doesn't help either. And last but not least, >> MI_FLUSH seems to work regardless of the setting of these bits." > > I haven't seen bit12 hanging snb/ivb -- I only knew of it hanging ilk > (since it doesn't exist there). On my snb, running xvideo so that > MI_FLUSHes are generated by the userland (I think -- I haven't caught > them in cat i915_batchbuffers | intel_dump_decode -), with > intel_reg_read 0x209c saying 0x1240, things are going fine. Also with > 0x209c saying 0x240 (the result of this patch). Daniel has a failing test on IVB. I haven't tried hard enough to make it fail on SNB, so I cannot speak to that. > > That 2008 PPT mentioned also said "the bit" and "bit 12", and only in > one cut-and-paste of a command line did I see it say two bits should be > set. I would trust the actual code more than a ppt. > > But basically, whatever we do to make this broken code go away, I'm fine > with. I'm in the same boat. I think trying to figure out which source to trust is a losing game for all, and our best bet is to find out what the Windows driver does, and presumably that cut-and-paste is not from the Windows driver. Ben
