[PATCH v3] drm/xe/guc: Enable WA_DUAL_QUEUE for newer platforms

[Daniele Ceraolo Spurio]

The DUAL_QUEUE_WA tells the GuC to not allow concurrent submissions
on RCS and CCSes with different address spaces, which on DG2 is
required as a WA for an HW bug. On newer platforms, this block has
been moved in HW at the CS level, by stalling the RCS/CCS context
switch when one of the other RCS/CCSes is busy with a different
address space. While functionally correct, having a submission
stalled on the HW limits the GuC ability to shuffle things around and
can cause complications if the non-stalled submission runs for a long
time, because the GuC doesn't know that the stalled submission isn't
actually running and might declare it as hung. Therefore, we enable
the DUAL_QUEUE_WA on all newer platforms to move management back to
the GuC.

Note that the GuC specs also recommend enabling this for all platforms
starting from MTL that have a CCS.

v2: only apply the WA on GTs that have CCS engines
v3: split comment (Jonathan)

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: John Harrison <John.C.Harrison at Intel.com>
Cc: Jesus Narvaez <jesus.narvaez at intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt at intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
---
 drivers/gpu/drm/xe/xe_guc.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
index 4e2868efb620..408365dfe4ee 100644
--- a/drivers/gpu/drm/xe/xe_guc.c
+++ b/drivers/gpu/drm/xe/xe_guc.c
@@ -147,6 +147,34 @@ static u32 guc_ctl_ads_flags(struct xe_guc *guc)
 	return flags;
 }
 
+static bool needs_wa_dual_queue(struct xe_gt *gt)
+{
+	/*
+	 * The DUAL_QUEUE_WA tells the GuC to not allow concurrent submissions
+	 * on RCS and CCSes with different address spaces, which on DG2 is
+	 * required as a WA for an HW bug.
+	 */
+	if (XE_WA(gt, 22011391025))
+		return true;
+
+	/*
+	 * On newer platforms, the HW has been updated to not allow parallel
+	 * execution of different address spaces, so the RCS/CCS will stall the
+	 * context switch if one of the other RCS/CCSes is busy with a different
+	 * address space. While functionally correct, having a submission
+	 * stalled on the HW limits the GuC ability to shuffle things around and
+	 * can cause complications if the non-stalled submission runs for a long
+	 * time, because the GuC doesn't know that the stalled submission isn't
+	 * actually running and might declare it as hung. Therefore, we enable
+	 * the DUAL_QUEUE_WA on all newer platforms on GTs that have CCS engines
+	 * to move management back to the GuC.
+	 */
+	if (CCS_MASK(gt) && GRAPHICS_VERx100(gt_to_xe(gt)) >= 1270)
+		return true;
+
+	return false;
+}
+
 static u32 guc_ctl_wa_flags(struct xe_guc *guc)
 {
 	struct xe_device *xe = guc_to_xe(guc);
@@ -159,7 +187,7 @@ static u32 guc_ctl_wa_flags(struct xe_guc *guc)
 	if (XE_WA(gt, 14014475959))
 		flags |= GUC_WA_HOLD_CCS_SWITCHOUT;
 
-	if (XE_WA(gt, 22011391025))
+	if (needs_wa_dual_queue(gt))
 		flags |= GUC_WA_DUAL_QUEUE;
 
 	/*
-- 
2.43.0