[Intel-xe] [PATCH 2/2] drm/xe: Add support for CCS engine fusing

[Matt Roper]

For Xe_HP platforms that can have multiple CCS engines, the
presence/absence of each CCS is inferred by the presence/absence of any
DSS in the corresponding quadrant of the GT's DSS mask.

This handling is only needed on platforms that can have more than one
CCS.  The CCS is never fused off on platforms like MTL that can only
have one.

Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/xe/xe_gt_topology.c | 47 +++++++++++++++++++++++------
 drivers/gpu/drm/xe/xe_gt_topology.h |  3 ++
 drivers/gpu/drm/xe/xe_hw_engine.c   | 29 +++++++++++++++++-
 3 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_gt_topology.c b/drivers/gpu/drm/xe/xe_gt_topology.c
index 2123f84be336..9f1930381d52 100644
--- a/drivers/gpu/drm/xe/xe_gt_topology.c
+++ b/drivers/gpu/drm/xe/xe_gt_topology.c
@@ -62,6 +62,21 @@ load_eu_mask(struct xe_gt *gt, xe_eu_mask_t mask)
 	bitmap_from_arr32(mask, &val, XE_MAX_EU_FUSE_BITS);
 }
 
+static void
+get_num_dss_regs(struct xe_device *xe, int *geometry_regs, int *compute_regs)
+{
+	if (GRAPHICS_VERx100(xe) == 1260) {
+		*geometry_regs = 0;
+		*compute_regs = 2;
+	} else if (GRAPHICS_VERx100(xe) >= 1250) {
+		*geometry_regs = 1;
+		*compute_regs = 1;
+	} else {
+		*geometry_regs = 1;
+		*compute_regs = 0;
+	}
+}
+
 void
 xe_gt_topology_init(struct xe_gt *gt)
 {
@@ -69,16 +84,7 @@ xe_gt_topology_init(struct xe_gt *gt)
 	struct drm_printer p = drm_debug_printer("GT topology");
 	int num_geometry_regs, num_compute_regs;
 
-	if (GRAPHICS_VERx100(xe) == 1260) {
-		num_geometry_regs = 0;
-		num_compute_regs = 2;
-	} else if (GRAPHICS_VERx100(xe) >= 1250) {
-		num_geometry_regs = 1;
-		num_compute_regs = 1;
-	} else {
-		num_geometry_regs = 1;
-		num_compute_regs = 0;
-	}
+	get_num_dss_regs(xe, &num_geometry_regs, &num_compute_regs);
 
 	load_dss_mask(gt, gt->fuse_topo.g_dss_mask, num_geometry_regs,
 		      XELP_GT_GEOMETRY_DSS_ENABLE.reg);
@@ -113,3 +119,24 @@ xe_dss_mask_group_ffs(xe_dss_mask_t mask, int groupsize, int groupnum)
 {
 	return find_next_bit(mask, XE_MAX_DSS_FUSE_BITS, groupnum * groupsize);
 }
+
+/*
+ * Determine whether the given quadrant has any DSS that are not fused off.
+ * Used to infer CCS engine availability on Xe_HP.
+ */
+bool xe_gt_topology_has_dss_in_quadrant(struct xe_gt *gt, int quad)
+{
+	struct xe_device *xe = gt_to_xe(gt);
+	xe_dss_mask_t all_dss;
+	int g_dss_regs, c_dss_regs, max_dss, quad_first;
+
+	bitmap_or(all_dss, gt->fuse_topo.g_dss_mask, gt->fuse_topo.c_dss_mask,
+		  XE_MAX_DSS_FUSE_BITS);
+
+	get_num_dss_regs(xe, &g_dss_regs, &c_dss_regs);
+	max_dss = 32 * max(g_dss_regs, c_dss_regs);
+
+	quad_first = xe_dss_mask_group_ffs(all_dss, max_dss / 4, quad);
+
+	return quad_first < (quad + 1) * max_dss / 4;
+}
diff --git a/drivers/gpu/drm/xe/xe_gt_topology.h b/drivers/gpu/drm/xe/xe_gt_topology.h
index b2540dc266f2..f47ab1b1269c 100644
--- a/drivers/gpu/drm/xe/xe_gt_topology.h
+++ b/drivers/gpu/drm/xe/xe_gt_topology.h
@@ -17,4 +17,7 @@ void xe_gt_topology_dump(struct xe_gt *gt, struct drm_printer *p);
 unsigned int
 xe_dss_mask_group_ffs(xe_dss_mask_t mask, int groupsize, int groupnum);
 
+bool
+xe_gt_topology_has_dss_in_quadrant(struct xe_gt *gt, int quad);
+
 #endif /* _XE_GT_TOPOLOGY_H_ */
diff --git a/drivers/gpu/drm/xe/xe_hw_engine.c b/drivers/gpu/drm/xe/xe_hw_engine.c
index ac00693ba0b2..f72f2e3b8c9a 100644
--- a/drivers/gpu/drm/xe/xe_hw_engine.c
+++ b/drivers/gpu/drm/xe/xe_hw_engine.c
@@ -436,13 +436,40 @@ static void read_copy_fuses(struct xe_gt *gt)
 	}
 }
 
+static void read_compute_fuses(struct xe_gt *gt)
+{
+	struct xe_device *xe = gt_to_xe(gt);
+
+	/*
+	 * CCS fusing based on DSS masks only applies to platforms that can
+	 * have more than one CCS.
+	 */
+	if (hweight32(gt->info.engine_mask &
+		      GENMASK(XE_HW_ENGINE_CCS3, XE_HW_ENGINE_CCS0)) <= 1)
+		return;
+
+	/*
+	 * CCS availability on Xe_HP is inferred from the presence of DSS in
+	 * each quadrant.
+	 */
+	for (int i = XE_HW_ENGINE_CCS0, j = 0; i <= XE_HW_ENGINE_CCS3; ++i, ++j) {
+		if (!(gt->info.engine_mask & BIT(i)))
+			continue;
+
+		if (!xe_gt_topology_has_dss_in_quadrant(gt, j)) {
+			gt->info.engine_mask &= ~BIT(i);
+			drm_info(&xe->drm, "ccs%u fused off\n", j);
+		}
+	}
+}
+
 int xe_hw_engines_init_early(struct xe_gt *gt)
 {
 	int i;
 
 	read_media_fuses(gt);
 	read_copy_fuses(gt);
-	/* TODO: compute engines */
+	read_compute_fuses(gt);
 
 	for (i = 0; i < ARRAY_SIZE(gt->hw_engines); i++)
 		hw_engine_init_early(gt, &gt->hw_engines[i], i);
-- 
2.39.2