Re: [PATCH v2 20/22] drm/xe/xe3p_xpc: Skip compression tuning on platforms without flatccs

[Gustavo Sousa <gustavo.sousa@intel.com>]

Quoting Lucas De Marchi (2025-10-15 19:06:35-03:00)
>From: Matt Roper <matthew.d.roper@intel.com>
>
>The compression overfetch tuning settings only apply to platforms that
>support FlatCCS.  In Xe3p_XPC (and any future IPs that also lack
>compression) some of the registers being adjusted by this tuning will
>not exist or may have been repurposed for something else, so we should
>take care not to try to program them.
>
>Note that our xe_rtp_match_has_flatccs() function will also return false
>on platforms that do have FlatCCS in the hardware design, but have
>compression manually disabled in the BIOS.  On such platforms the
>registers still exist (and it would be fine to continue programming
>them), but they would have no effect, so skipping that tuning is also
>safe.
>
>Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
>Reviewed-by: Shekhar Chauhan <shekhar.chauhan@intel.com>
>Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
>---
> drivers/gpu/drm/xe/xe_rtp.c    |  7 +++++++
> drivers/gpu/drm/xe/xe_rtp.h    | 12 ++++++++++++
> drivers/gpu/drm/xe/xe_tuning.c |  9 ++++++---
> 3 files changed, 25 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_rtp.c b/drivers/gpu/drm/xe/xe_rtp.c
>index 66707cc89ec97..ed509b1c8cfcd 100644
>--- a/drivers/gpu/drm/xe/xe_rtp.c
>+++ b/drivers/gpu/drm/xe/xe_rtp.c
>@@ -378,3 +378,10 @@ bool xe_rtp_match_gt_has_discontiguous_dss_groups(const struct xe_device *xe,
> {
>         return xe_gt_has_discontiguous_dss_groups(gt);
> }
>+
>+bool xe_rtp_match_has_flat_ccs(const struct xe_device *xe,
>+                               const struct xe_gt *gt,
>+                               const struct xe_hw_engine *hwe)
>+{
>+        return xe->info.has_flat_ccs;
>+}

One possible issue here is that OOB RTP entries are processed before we
call probe_has_flat_ccs().  Not a real problem right now, because we are
only using xe_rtp_match_has_flat_ccs() in gt_tunnings, but this could be
problematic if in the future someone added a
FUNC(xe_rtp_match_has_flat_ccs) in OOB rules files.

--
Gustavo Sousa

>diff --git a/drivers/gpu/drm/xe/xe_rtp.h b/drivers/gpu/drm/xe/xe_rtp.h
>index e5b8a9452e29e..ba5f940c0a961 100644
>--- a/drivers/gpu/drm/xe/xe_rtp.h
>+++ b/drivers/gpu/drm/xe/xe_rtp.h
>@@ -491,4 +491,16 @@ bool xe_rtp_match_gt_has_discontiguous_dss_groups(const struct xe_device *xe,
>                                                   const struct xe_gt *gt,
>                                                   const struct xe_hw_engine *hwe);
> 
>+/**
>+ * xe_rtp_match_has_flat_ccs - Match when platform has FlatCCS compression
>+ * @xe: Device structure
>+ * @gt: GT structure
>+ * @hwe: Engine instance
>+ *
>+ * Returns: true if platform has FlatCCS compression, false otherwise
>+ */
>+bool xe_rtp_match_has_flat_ccs(const struct xe_device *xe,
>+                               const struct xe_gt *gt,
>+                               const struct xe_hw_engine *hwe);
>+
> #endif
>diff --git a/drivers/gpu/drm/xe/xe_tuning.c b/drivers/gpu/drm/xe/xe_tuning.c
>index fd58ea5e78bf6..7c140d8cb1e07 100644
>--- a/drivers/gpu/drm/xe/xe_tuning.c
>+++ b/drivers/gpu/drm/xe/xe_tuning.c
>@@ -40,7 +40,8 @@ static const struct xe_rtp_entry_sr gt_tunings[] = {
>                                    REG_FIELD_PREP(L3_PWM_TIMER_INIT_VAL_MASK, 0x7f)))
>         },
>         { XE_RTP_NAME("Tuning: Compression Overfetch"),
>-          XE_RTP_RULES(GRAPHICS_VERSION_RANGE(2001, XE_RTP_END_VERSION_UNDEFINED)),
>+          XE_RTP_RULES(GRAPHICS_VERSION_RANGE(2001, XE_RTP_END_VERSION_UNDEFINED),
>+                       FUNC(xe_rtp_match_has_flat_ccs)),
>           XE_RTP_ACTIONS(CLR(CCCHKNREG1, ENCOMPPERFFIX),
>                          SET(CCCHKNREG1, L3CMPCTRL))
>         },
>@@ -58,12 +59,14 @@ static const struct xe_rtp_entry_sr gt_tunings[] = {
>           XE_RTP_ACTIONS(SET(XE2LPM_L3SQCREG3, COMPPWOVERFETCHEN))
>         },
>         { XE_RTP_NAME("Tuning: L2 Overfetch Compressible Only"),
>-          XE_RTP_RULES(GRAPHICS_VERSION_RANGE(2001, XE_RTP_END_VERSION_UNDEFINED)),
>+          XE_RTP_RULES(GRAPHICS_VERSION_RANGE(2001, XE_RTP_END_VERSION_UNDEFINED),
>+                       FUNC(xe_rtp_match_has_flat_ccs)),
>           XE_RTP_ACTIONS(SET(L3SQCREG2,
>                              COMPMEMRD256BOVRFETCHEN))
>         },
>         { XE_RTP_NAME("Tuning: L2 Overfetch Compressible Only - media"),
>-          XE_RTP_RULES(MEDIA_VERSION_RANGE(2000, XE_RTP_END_VERSION_UNDEFINED)),
>+          XE_RTP_RULES(MEDIA_VERSION_RANGE(2000, XE_RTP_END_VERSION_UNDEFINED),
>+                       FUNC(xe_rtp_match_has_flat_ccs)),
>           XE_RTP_ACTIONS(SET(XE2LPM_L3SQCREG2,
>                              COMPMEMRD256BOVRFETCHEN))
>         },
>
>-- 
>2.51.0
>