From: Andi Shyti <andi.shyti@linux.intel.com>
To: intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>
Cc: Chris Wilson <chris.p.wilson@linux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Matt Roper <matthew.d.roper@intel.com>,
	John Harrison <John.C.Harrison@Intel.com>,
	stable@vger.kernel.org,
	Andi Shyti <andi.shyti@linux.intel.com>,
	Andi Shyti <andi.shyti@kernel.org>,
	Tvrtko Ursulin <tursulin@ursulin.net>
Subject: [PATCH v8 1/3] drm/i915/gt: Disable HW load balancing for CCS
Date: Thu, 28 Mar 2024 08:34:03 +0100
Message-ID: <20240328073409.674098-2-andi.shyti@linux.intel.com>
In-Reply-To: <20240328073409.674098-1-andi.shyti@linux.intel.com>
References: <20240328073409.674098-1-andi.shyti@linux.intel.com>
Precedence: bulk
MIME-Version: 1.0
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The hardware should not dynamically balance the load between CCS
engines. Wa_14019159160 recommends disabling it across all
platforms.

Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Chris Wilson <chris.p.wilson@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: <stable@vger.kernel.org> # v6.2+
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Michal Mrozek <michal.mrozek@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_gt_regs.h     |  1 +
 drivers/gpu/drm/i915/gt/intel_workarounds.c | 23 +++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
index 731ed3ecd9a6..f8829be40199 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
@@ -1424,6 +1424,7 @@
 #define   ECOBITS_PPGTT_CACHE4B			(0 << 8)
 
 #define GEN12_RCU_MODE				_MMIO(0x14800)
+#define   XEHP_RCU_MODE_FIXED_SLICE_CCS_MODE	REG_BIT(1)
 #define   GEN12_RCU_MODE_CCS_ENABLE		REG_BIT(0)
 
 #define CHV_FUSE_GT				_MMIO(VLV_GUNIT_BASE + 0x2168)
diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
index de5fe26bb18e..74cf678b7589 100644
--- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
@@ -51,7 +51,8 @@
  *   registers belonging to BCS, VCS or VECS should be implemented in
  *   xcs_engine_wa_init(). Workarounds for registers not belonging to a specific
  *   engine's MMIO range but that are part of of the common RCS/CCS reset domain
- *   should be implemented in general_render_compute_wa_init().
+ *   should be implemented in general_render_compute_wa_init(). The settings
+ *   about the CCS load balancing should be added in ccs_engine_wa_mode().
  *
  * - GT workarounds: the list of these WAs is applied whenever these registers
  *   revert to their default values: on GPU reset, suspend/resume [1]_, etc.
@@ -2698,6 +2699,22 @@ add_render_compute_tuning_settings(struct intel_gt *gt,
 		wa_write_clr(wal, GEN8_GARBCNTL, GEN12_BUS_HASH_CTL_BIT_EXC);
 }
 
+static void ccs_engine_wa_mode(struct intel_engine_cs *engine, struct i915_wa_list *wal)
+{
+	struct intel_gt *gt = engine->gt;
+
+	if (!IS_DG2(gt->i915))
+		return;
+
+	/*
+	 * Wa_14019159160: This workaround, along with others, leads to
+	 * significant challenges in utilizing load balancing among the
+	 * CCS slices. Consequently, an architectural decision has been
+	 * made to completely disable automatic CCS load balancing.
+	 */
+	wa_masked_en(wal, GEN12_RCU_MODE, XEHP_RCU_MODE_FIXED_SLICE_CCS_MODE);
+}
+
 /*
  * The workarounds in this function apply to shared registers in
  * the general render reset domain that aren't tied to a
@@ -2830,8 +2847,10 @@ engine_init_workarounds(struct intel_engine_cs *engine, struct i915_wa_list *wal
 	 * to a single RCS/CCS engine's workaround list since
 	 * they're reset as part of the general render domain reset.
 	 */
-	if (engine->flags & I915_ENGINE_FIRST_RENDER_COMPUTE)
+	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_init(engine, wal);
-- 
2.43.0