[Intel-gfx] [PATCH v3] drm/i915/icl: Support co-existence between per-context SSEU and OA

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

When OA is active we want to lock the powergating configuration, but on
Icelake, users like the media stack will have issues if we lock to the
full device configuration.

Instead lock to a subset of (sub)slices which are currently a known
working configuration for all users.

v2:
 * Fix commit message spelling.

v3:
 Lionel:
 * Add bspec reference.
 * Fix spelling in comment.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Bspec: 21140
Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index c6c5938684cf..2e8151192fc4 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2577,13 +2577,28 @@ u32 gen8_make_rpcs(struct drm_i915_private *i915, struct intel_sseu *req_sseu)
 
 	/*
 	 * If i915/perf is active, we want a stable powergating configuration
-	 * on the system. The most natural configuration to take in that case
-	 * is the default (i.e maximum the hardware can do).
+	 * on the system.
+	 *
+	 * We could choose full enablement, but on ICL we know there are use
+	 * cases which disable slices for functional, apart for performance
+	 * reasons. So in this case we select a known stable subset.
 	 */
-	if (unlikely(i915->perf.oa.exclusive_stream))
-		ctx_sseu = intel_device_default_sseu(i915);
-	else
+	if (!i915->perf.oa.exclusive_stream) {
 		ctx_sseu = *req_sseu;
+	} else {
+		ctx_sseu = intel_device_default_sseu(i915);
+
+		if (IS_GEN11(i915)) {
+			/*
+			 * We only need subslice count so it doesn't matter
+			 * which ones we select - just turn off low bits in the
+			 * amount of half of all available subslices per slice.
+			 */
+			ctx_sseu.subslice_mask =
+				~(~0 << (hweight8(ctx_sseu.subslice_mask) / 2));
+			ctx_sseu.slice_mask = 0x1;
+		}
+	}
 
 	slices = hweight8(ctx_sseu.slice_mask);
 	subslices = hweight8(ctx_sseu.subslice_mask);
-- 
2.17.1