On Tue, Mar 25, 2025 at 01:57:42PM +0100, Chris Wilson wrote:
> Quoting Andi Shyti (2025-03-25 13:01:37)
> > When generating workarounds for the CCS engine, specifically for
> > setting the CCS mode related to compute load balancing, the
> > function 'ccs_engine_wa_mode()' is called twice: once for the
> > render engine and once for the compute engine.
> >
> > Add a check to ensure the engine class is compute before applying
> > the workaround to avoid redundant programming.
> >
> > Suggested-by: Arshad Mehmood <arshad.mehm...@intel.com>
> > Signed-off-by: Andi Shyti <andi.sh...@linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/gt/intel_workarounds.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > index 116683ebe074..37251546b755 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > @@ -2897,7 +2897,9 @@ engine_init_workarounds(struct intel_engine_cs
> > *engine, struct i915_wa_list *wal
> > */
> > if (engine->flags & I915_ENGINE_FIRST_RENDER_COMPUTE) {
> > general_render_compute_wa_init(engine, wal);
> > - ccs_engine_wa_mode(engine, wal);
> > +
> > + if (engine->class == COMPUTE_CLASS)
> > + ccs_engine_wa_mode(engine, wal);
>
> FIRST_RENDER_COMPUTE is meant to only be on the first engine of either
> rcs or ccs (which share certain register domains), one engine.
>
> It looks like that was broken by
>
> commit 1bfc03b1375244f9029bb448ee8224b3b6dae99f
> Author: Lucas De Marchi <lucas.demar...@intel.com>
> Date: Tue Mar 19 23:03:03 2024 -0700
>
> drm/i915: Remove special handling for !RCS_MASK()
Aha! So the logic here[*] breaks the meaning of
I915_ENGINE_FIRST_RENDER_COMPUTE, becasue, other than PVC, we
forgot that we have DG2 that needs the special check that uses
!RCS_MASK().
I need then to restore the original check.
Thanks Chris!
Andi
[*]
- if ((engine->class == COMPUTE_CLASS && !RCS_MASK(engine->gt) &&
- __ffs(CCS_MASK(engine->gt)) == engine->instance) ||
- engine->class == RENDER_CLASS)
+ if ((engine->class == COMPUTE_CLASS || engine->class == RENDER_CLASS) &&
+ __ffs(CCS_MASK(engine->gt) | RCS_MASK(engine->gt)) ==
engine->instance)
