drm/i915/selftests: ring all doorbells in igt_guc_doorbells

We currently verify that all doorbells can be registered with GuC and
HW but don't check that all works as expected after a db ring.

Do a nop ring of all doorbells to make sure we haven't misprogrammed
any WQ or stage descriptor data. This will also help validating
upcoming changes in the db programming flow.

Cc: Michel Thierry <[e-mail]>
Cc: Michal Wajdeczko <[e-mail]>
Signed-off-by: Daniele Ceraolo Spurio <[e-mail]>
Reviewed-by: Michel Thierry <[e-mail]>
Acked-by: Katarzyna Dec <[e-mail]>
Signed-off-by: Chris Wilson <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/intel_guc_fwif.h

···
 #define   WQ_TYPE_BATCH_BUF		(0x1 << WQ_TYPE_SHIFT)
 #define   WQ_TYPE_PSEUDO		(0x2 << WQ_TYPE_SHIFT)
 #define   WQ_TYPE_INORDER		(0x3 << WQ_TYPE_SHIFT)
+#define   WQ_TYPE_NOOP			(0x4 << WQ_TYPE_SHIFT)
 #define WQ_TARGET_SHIFT			10
 #define WQ_LEN_SHIFT			16
 #define WQ_NO_WCFLUSH_WAIT		(1 << 27)

drivers/gpu/drm/i915/intel_guc_submission.c

···
 	 */
 	BUILD_BUG_ON(wqi_size != 16);
 
+	/* We expect the WQ to be active if we're appending items to it */
+	GEM_BUG_ON(desc->wq_status != WQ_STATUS_ACTIVE);
+
 	/* Free space is guaranteed. */
 	wq_off = READ_ONCE(desc->tail);
 	GEM_BUG_ON(CIRC_SPACE(wq_off, READ_ONCE(desc->head),
···
 	/* WQ starts from the page after doorbell / process_desc */
 	wqi = client->vaddr + wq_off + GUC_DB_SIZE;
 
-	/* Now fill in the 4-word work queue item */
-	wqi->header = WQ_TYPE_INORDER |
-		      (wqi_len << WQ_LEN_SHIFT) |
-		      (target_engine << WQ_TARGET_SHIFT) |
-		      WQ_NO_WCFLUSH_WAIT;
-	wqi->context_desc = context_desc;
-	wqi->submit_element_info = ring_tail << WQ_RING_TAIL_SHIFT;
-	GEM_BUG_ON(ring_tail > WQ_RING_TAIL_MAX);
-	wqi->fence_id = fence_id;
+	if (I915_SELFTEST_ONLY(client->use_nop_wqi)) {
+		wqi->header = WQ_TYPE_NOOP | (wqi_len << WQ_LEN_SHIFT);
+	} else {
+		/* Now fill in the 4-word work queue item */
+		wqi->header = WQ_TYPE_INORDER |
+			      (wqi_len << WQ_LEN_SHIFT) |
+			      (target_engine << WQ_TARGET_SHIFT) |
+			      WQ_NO_WCFLUSH_WAIT;
+		wqi->context_desc = context_desc;
+		wqi->submit_element_info = ring_tail << WQ_RING_TAIL_SHIFT;
+		GEM_BUG_ON(ring_tail > WQ_RING_TAIL_MAX);
+		wqi->fence_id = fence_id;
+	}
 
 	/* Make the update visible to GuC */
 	WRITE_ONCE(desc->tail, (wq_off + wqi_size) & (GUC_WQ_SIZE - 1));

drivers/gpu/drm/i915/intel_guc_submission.h

···
 #include <linux/spinlock.h>
 
 #include "i915_gem.h"
+#include "i915_selftest.h"
 
 struct drm_i915_private;
 
···
 	spinlock_t wq_lock;
 	/* Per-engine counts of GuC submissions */
 	u64 submissions[I915_NUM_ENGINES];
+
+	/* For testing purposes, use nop WQ items instead of real ones */
+	I915_SELFTEST_DECLARE(bool use_nop_wqi);
 };
 
 int intel_guc_submission_init(struct intel_guc *guc);

drivers/gpu/drm/i915/selftests/intel_guc.c

···
 	return 0;
 }
 
+static int ring_doorbell_nop(struct intel_guc_client *client)
+{
+	struct guc_process_desc *desc = __get_process_desc(client);
+	int err;
+
+	client->use_nop_wqi = true;
+
+	spin_lock_irq(&client->wq_lock);
+
+	guc_wq_item_append(client, 0, 0, 0, 0);
+	guc_ring_doorbell(client);
+
+	spin_unlock_irq(&client->wq_lock);
+
+	client->use_nop_wqi = false;
+
+	/* if there are no issues GuC will update the WQ head and keep the
+	 * WQ in active status
+	 */
+	err = wait_for(READ_ONCE(desc->head) == READ_ONCE(desc->tail), 10);
+	if (err) {
+		pr_err("doorbell %u ring failed!\n", client->doorbell_id);
+		return -EIO;
+	}
+
+	if (desc->wq_status != WQ_STATUS_ACTIVE) {
+		pr_err("doorbell %u ring put WQ in bad state (%u)!\n",
+		       client->doorbell_id, desc->wq_status);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 /*
  * Basic client sanity check, handy to validate create_clients.
  */
···
 		}
 
 		err = check_all_doorbells(guc);
+		if (err)
+			goto out;
+
+		err = ring_doorbell_nop(clients[i]);
 		if (err)
 			goto out;
 	}