On 12/10/2021 21:30, Lucas De Marchi wrote:
On Fri, Dec 10, 2021 at 05:41:46PM -0800, John Harrison wrote:
On 12/10/2021 17:22, Matt Roper wrote:
On Thu, Dec 09, 2021 at 09:21:39AM -0800, Lucas De Marchi wrote:
On Fri, Dec 03, 2021 at 08:26:03PM +0530,
ravitejax.goud.talla@xxxxxxxxx wrote:
From: Raviteja Goud Talla <ravitejax.goud.talla@xxxxxxxxx>
Bspec page says "Reset: BUS", Accordingly moving w/a's:
Wa_1407352427,Wa_1406680159 to proper function
icl_gt_workarounds_init()
Which will resolve guc enabling error
v2:
- Previous patch rev2 was created by email client which caused the
Build failure, This v2 is to resolve the previous broken series
Reviewed-by: John Harrison <John.C.Harrison@xxxxxxxxx>
Signed-off-by: Raviteja Goud Talla <ravitejax.goud.talla@xxxxxxxxx>
It seems like this patch is needed to be able to load GuC in ICL:
https://gitlab.freedesktop.org/drm/intel/-/issues/4067#note_1184951
And that is failing on Linus' master branch as of
2a987e65025e ("Merge tag 'perf-tools-fixes-for-v5.16-2021-12-07' of
git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux")
and (at least) 5.15.*. Looking at the appropriate "Fixes" tag I
found these commits:
1) 1cd21a7c5679 ("drm/i915: Add Wa_1407352427:icl,ehl") - original
commit adding the WA
2) 3551ff928744 ("drm/i915/gen11: Moving WAs to
rcs_engine_wa_init()")
moving the WA to rcs_engine_wa_init()
However (2) is on v5.7-rc1 and (1) is on v5.6-rc1 and according to the
bug report GuC loading was working on 5.13. So I suspect the move
to GuC 62.0.0 made the checks more strict, or there is another patch
This is correct. Having "GT workarounds" on the engine list by
accident
used to be harmless (because i915 [with execlist submission] and the
guc
[with guc submission]) would simply re-apply the register setting more
often than it really needed to. However the more recent GuC versions
have become more picky about the set of registers they're willing to
Actually, I think the GuC was always picky but we haven't supported
GuC submission upstream for quite some time. There was very old
support (never enabled by default) in the VLV timescale. And at that
time, we were not using GuC scheduling anyway, so no save/restore
list. I think by ICL it had already been removed as broken. All you
could do was load the GuC in order to load the HuC. It is only
recently with the ADL-P/DG1 support that GuC submission has been
re-implemented and the save/restore list added in.
as I said in my other reply to Matt, it's not GuC sumbmission that got
broken though: it's enable_guc=2.
My point is that it wasn't broken until we added the GuC submission
support. Doesn't matter whether submission is enabled or not. Until it
was implemented, there was no save/restore list. After it was
implemented, the list was created even for enable_guc=2 as it is part of
initialising the GuC.
John.
save/restore for workarounds and will fail to load if they see a
register on the save/restore list that isn't something they think is
appropriate for an engine reset.
GuC submission isn't officially supported on ICL; you can force it via
module parameter, which taints the kernel and takes you through
untested
codepaths, so you do so at your own risk. Given that, I don't think
there's any real need to worry about getting this backported to
specific
stable kernels; having the workaround in the wrong place doesn't
actually harm anything on the official and default non-GuC mode.
As above, even with GuC enabled, I still don't think it is a problem
for any kernel using a GuC version earlier than 62.0.0.
so that rules out 5.10 and the only stable we need this on is 5.15 which
is pretty easy and applies cleanly.
Lucas De Marchi
