drm/i915/gt: Enable only one CCS for compute workload

Enable only one CCS engine by default with all the compute sices
allocated to it.

While generating the list of UABI engines to be exposed to the
user, exclude any additional CCS engines beyond the first
instance.

This change can be tested with igt i915_query.

Fixes: d2eae8e9 ("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>
Link: https://patchwork.freedesktop.org/patch/msgid/20240328073409.674098-4-andi.shyti@linux.intel.com

drivers/gpu/drm/i915/Makefile

@@ -118,6 +118,7 @@ gt-y += \
 	gt/intel_ggtt_fencing.o \
 	gt/intel_gt.o \
 	gt/intel_gt_buffer_pool.o \
+	gt/intel_gt_ccs_mode.o \
 	gt/intel_gt_clock_utils.o \
 	gt/intel_gt_debugfs.o \
 	gt/intel_gt_engines_debugfs.o \

drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c

+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include "i915_drv.h"
+#include "intel_gt.h"
+#include "intel_gt_ccs_mode.h"
+#include "intel_gt_regs.h"
+
+void intel_gt_apply_ccs_mode(struct intel_gt *gt)
+{
+	int cslice;
+	u32 mode = 0;
+	int first_ccs = __ffs(CCS_MASK(gt));
+
+	if (!IS_DG2(gt->i915))
+		return;
+
+	/* Build the value for the fixed CCS load balancing */
+	for (cslice = 0; cslice < I915_MAX_CCS; cslice++) {
+		if (CCS_MASK(gt) & BIT(cslice))
+			/*
+			 * If available, assign the cslice
+			 * to the first available engine...
+			 */
+			mode |= XEHP_CCS_MODE_CSLICE(cslice, first_ccs);
+
+		else
+			/*
+			 * ... otherwise, mark the cslice as
+			 * unavailable if no CCS dispatches here
+			 */
+			mode |= XEHP_CCS_MODE_CSLICE(cslice,
+						     XEHP_CCS_MODE_CSLICE_MASK);
+	}
+
+	intel_uncore_write(gt->uncore, XEHP_CCS_MODE, mode);
+}

drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.h

+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef __INTEL_GT_CCS_MODE_H__
+#define __INTEL_GT_CCS_MODE_H__
+
+struct intel_gt;
+
+void intel_gt_apply_ccs_mode(struct intel_gt *gt);
+
+#endif /* __INTEL_GT_CCS_MODE_H__ */

drivers/gpu/drm/i915/gt/intel_gt_regs.h

@@ -1481,6 +1481,11 @@
 #define   XEHP_RCU_MODE_FIXED_SLICE_CCS_MODE	REG_BIT(1)
 #define   GEN12_RCU_MODE_CCS_ENABLE		REG_BIT(0)
 
+#define XEHP_CCS_MODE				_MMIO(0x14804)
+#define   XEHP_CCS_MODE_CSLICE_MASK		REG_GENMASK(2, 0) /* CCS0-3 + rsvd */
+#define   XEHP_CCS_MODE_CSLICE_WIDTH		ilog2(XEHP_CCS_MODE_CSLICE_MASK + 1)
+#define   XEHP_CCS_MODE_CSLICE(cslice, ccs)	(ccs << (cslice * XEHP_CCS_MODE_CSLICE_WIDTH))
+
 #define CHV_FUSE_GT				_MMIO(VLV_GUNIT_BASE + 0x2168)
 #define   CHV_FGT_DISABLE_SS0			(1 << 10)
 #define   CHV_FGT_DISABLE_SS1			(1 << 11)

drivers/gpu/drm/i915/gt/intel_workarounds.c

@@ -10,6 +10,7 @@
 #include "intel_engine_regs.h"
 #include "intel_gpu_commands.h"
 #include "intel_gt.h"
+#include "intel_gt_ccs_mode.h"
 #include "intel_gt_mcr.h"
 #include "intel_gt_print.h"
 #include "intel_gt_regs.h"
@@ -2868,6 +2869,12 @@ static void ccs_engine_wa_mode(struct intel_engine_cs *engine, struct i915_wa_li
 	 * made to completely disable automatic CCS load balancing.
 	 */
 	wa_masked_en(wal, GEN12_RCU_MODE, XEHP_RCU_MODE_FIXED_SLICE_CCS_MODE);
+
+	/*
+	 * After having disabled automatic load balancing we need to
+	 * assign all slices to a single CCS. We will call it CCS mode 1
+	 */
+	intel_gt_apply_ccs_mode(gt);
 }
 
 /*