[PATCH 1/4] drm/xe: Fix GT "for each engine" workarounds

[Matt Roper]

On Wed, Feb 26, 2025 at 11:20:16AM -0600, Lucas De Marchi wrote:
> On Wed, Feb 26, 2025 at 11:21:03AM +0000, Tvrtko Ursulin wrote:
> > Any rules using engine matching are currently broken due RTP processing
> > happening too in early init, before the list of hardware engines has been
> > initialised.
> > 
> > Fix this by moving workaround processing to later in the driver probe
> > sequence, to just before the processed list is used for the first time.
> > 
> > Looking at the debugfs gt0/workarounds on ADL-P we notice 14011060649
> > should be present while we see, before:
> > 
> > GT Workarounds
> >     14011059788
> >     14015795083
> > 
> > And with the patch:
> > 
> > GT Workarounds
> >     14011060649
> >     14011059788
> >     14015795083
> > 
> > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> > Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> > Cc: Matt Roper <matthew.d.roper at intel.com>
> 
> Cc: <stable at vger.kernel.org> # v6.11+
> Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com>
> 
> The version in Cc stable is because it's what matters for officially
> supported HW by xe.
> 
> We've been using the reset domain to decide if a WA is an engine vs gt
> workaround. Although I'm thinking if it wouldn't be better to simply
> drop the FOREACH_ENGINE processing and move those workarounds to be
> engine workarounds. Matt, any thoughts?

That's a common mistake we've made in the past --- it doesn't work.  If
you try to put a bunch of these registers onto the GuC's save/restore
list as happens with engine workarounds, the GuC will throw an assertion
and fail to load because it considers them to be outside the very narrow
set of register ranges it's allowed to work with.

So no, unfortunately these do need to remain "GT" workarounds, even
though they need to be applied to registers that have per-engine
instances.  :-(


Matt

> 
> thanks
> Lucas De Marchi
> 
> > ---
> > drivers/gpu/drm/xe/xe_gt.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
> > index 650a0ee56e97..d59c03bc05b7 100644
> > --- a/drivers/gpu/drm/xe/xe_gt.c
> > +++ b/drivers/gpu/drm/xe/xe_gt.c
> > @@ -361,9 +361,7 @@ int xe_gt_init_early(struct xe_gt *gt)
> > 	if (err)
> > 		return err;
> > 
> > -	xe_wa_process_gt(gt);
> > 	xe_wa_process_oob(gt);
> > -	xe_tuning_process_gt(gt);
> > 
> > 	xe_force_wake_init_gt(gt, gt_to_fw(gt));
> > 	spin_lock_init(&gt->global_invl_lock);
> > @@ -450,6 +448,8 @@ static int all_fw_domain_init(struct xe_gt *gt)
> > 	}
> > 
> > 	xe_gt_mcr_set_implicit_defaults(gt);
> > +	xe_wa_process_gt(gt);
> > +	xe_tuning_process_gt(gt);
> > 	xe_reg_sr_apply_mmio(&gt->reg_sr, gt);
> > 
> > 	err = xe_gt_clock_init(gt);
> > -- 
> > 2.48.0
> > 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation