drm/i915/gt: Do not generate the command streamer for all the CCS

We want a fixed load CCS balancing consisting in all slices
sharing one single user engine. For this reason do not create the
intel_engine_cs structure with its dedicated command streamer for
CCS slices beyond the first.

Fixes: d2eae8e ("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+
Acked-by: Michal Mrozek <michal.mrozek@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240328073409.674098-3-andi.shyti@linux.intel.com

Author: Andi Shyti

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

@@ -908,6 +908,23 @@ static intel_engine_mask_t init_engine_mask(struct intel_gt *gt)
 		info->engine_mask &= ~BIT(GSC0);
 	}
 
+	/*
+	 * Do not create the command streamer for CCS slices beyond the first.
+	 * All the workload submitted to the first engine will be shared among
+	 * all the slices.
+	 *
+	 * Once the user will be allowed to customize the CCS mode, then this
+	 * check needs to be removed.
+	 */
+	if (IS_DG2(gt->i915)) {
+		u8 first_ccs = __ffs(CCS_MASK(gt));
+
+		/* Mask off all the CCS engine */
+		info->engine_mask &= ~GENMASK(CCS3, CCS0);
+		/* Put back in the first CCS engine */
+		info->engine_mask |= BIT(_CCS(first_ccs));
+	}
+
 	return info->engine_mask;
 }