On 01/24/12 18:55, Eric Anholt wrote:
On Sat, 21 Jan 2012 17:36:13 +0100, Daniel Vetter<dan...@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<e...@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
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