[PATCH] drm/xe/ptl: Disable null query for anyhit shader

[Gote, Nitin R]

Hi Matt,

> On Wed, May 07, 2025 at 10:50:20AM -0300, Gustavo Sousa wrote:
> > Quoting Nitin Gote (2025-05-07 09:44:37-03:00)
> > >For PTL, disable null query for anyhit shader as it currently does
> > >not bring any performance benefits.
> > >Quite the contrary, disabling the mechanism brings a small but
> > >consistent perf uplift.
> > >
> > >Signed-off-by: Nitin Gote <nitin.r.gote at intel.com>
> >
> > This seems to match the requirements for Xe3 according to the
> > description of RT_CTL. So
> 
> Doesn't the description (on bspec 57496) indicate that it applies to everything Xe2
> and beyond?  I don't see anything there about Xe3 specifically.  In that case
> something like GRAPHICS_VERSION_RANGE(2000,
> XE_RTP_END_VERSION_UNDEFINED) would be more accurate reflection of that
> note.
> 
> But that bspec page also indicates that '1' is already the hardware default value
> on all such platforms, so this patch doesn't seem necessary if the spec is correct.
> 

You are right.
I read the register and found out that the default value is 1. So, this patch might not be required.
I will check with the HW team.

Thank you Matt and Gustavo for the review.

- Nitin

> 
> Matt
> 
> >
> > Reviewed-by: Gustavo Sousa <gustavo.sousa at intel.com>
> >
> > However, we usually have entries in Bspec 72161 for this kind of stuff.
> > Could we get that page updated with a proper entry for this tuning,
> > please?
> >
> > Also, I would use "drm/xe/xe3:" in the commit subject, since this is
> > applicable to the Xe3 IP and not necessarily specific to the platform.
> >
> > --
> > Gustavo Sousa
> >
> > >---
> > > drivers/gpu/drm/xe/xe_tuning.c | 5 +++++
> > > 1 file changed, 5 insertions(+)
> > >
> > >diff --git a/drivers/gpu/drm/xe/xe_tuning.c
> > >b/drivers/gpu/drm/xe/xe_tuning.c index 49ddbda7cdef..6f2f3428b12e
> > >100644
> > >--- a/drivers/gpu/drm/xe/xe_tuning.c
> > >+++ b/drivers/gpu/drm/xe/xe_tuning.c
> > >@@ -98,6 +98,11 @@ static const struct xe_rtp_entry_sr engine_tunings[] = {
> > >                        ENGINE_CLASS(RENDER)),
> > >           XE_RTP_ACTIONS(SET(SAMPLER_MODE,
> INDIRECT_STATE_BASE_ADDR_OVERRIDE))
> > >         },
> > >+        { XE_RTP_NAME("Tuning: Disable NULL query for Anyhit Shader"),
> > >+          XE_RTP_RULES(GRAPHICS_VERSION_RANGE(3000, 3001),
> > >+                       FUNC(xe_rtp_match_first_render_or_compute)),
> > >+          XE_RTP_ACTIONS(SET(RT_CTRL, DIS_NULL_QUERY))
> > >+        },
> > > };
> > >
> > > static const struct xe_rtp_entry_sr lrc_tunings[] = {
> > >--
> > >2.25.1
> > >
> 
> --
> Matt Roper
> Graphics Software Engineer
> Linux GPU Platform Enablement
> Intel Corporation