drm/xe: Prep TLB invalidation fence before sending

It is a bit backwards to add a TLB invalidation fence to the pending
list after issuing the invalidation. Perform this step before issuing
the TLB invalidation in a helper function.

v2: Make sure the seqno_lock mutex covers the send as well (Matt)

Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250826182911.392550-8-stuart.summers@intel.com

Author: mbrost05

drivers/gpu/drm/xe/xe_tlb_inval.c

@@ -66,19 +66,19 @@ __inval_fence_signal(struct xe_device *xe, struct xe_tlb_inval_fence *fence)
 static void
 inval_fence_signal(struct xe_device *xe, struct xe_tlb_inval_fence *fence)
 {
+	lockdep_assert_held(&fence->tlb_inval->pending_lock);
+
 	list_del(&fence->link);
 	__inval_fence_signal(xe, fence);
 }
 
-void xe_tlb_inval_fence_signal(struct xe_tlb_inval_fence *fence)
+static void
+inval_fence_signal_unlocked(struct xe_device *xe,
+			    struct xe_tlb_inval_fence *fence)
 {
-	struct xe_gt *gt;
-
-	if (WARN_ON_ONCE(!fence->tlb_inval))
-		return;
-
-	gt = fence->tlb_inval->private;
-	__inval_fence_signal(gt_to_xe(gt), fence);
+	spin_lock_irq(&fence->tlb_inval->pending_lock);
+	inval_fence_signal(xe, fence);
+	spin_unlock_irq(&fence->tlb_inval->pending_lock);
 }
 
 static void xe_gt_tlb_fence_timeout(struct work_struct *work)
@@ -221,14 +221,10 @@ static bool tlb_inval_seqno_past(struct xe_gt *gt, int seqno)
 	return seqno_recv >= seqno;
 }
 
-static int send_tlb_inval(struct xe_guc *guc,
-			  struct xe_tlb_inval_fence *fence,
+static int send_tlb_inval(struct xe_guc *guc, struct xe_tlb_inval_fence *fence,
 			  u32 *action, int len)
 {
 	struct xe_gt *gt = guc_to_gt(guc);
-	struct xe_device *xe = gt_to_xe(gt);
-	int seqno;
-	int ret;
 
 	xe_gt_assert(gt, fence);
 
@@ -238,47 +234,36 @@ static int send_tlb_inval(struct xe_guc *guc,
 	 * need to be updated.
 	 */
 
-	mutex_lock(&gt->tlb_inval.seqno_lock);
-	seqno = gt->tlb_inval.seqno;
-	fence->seqno = seqno;
-	trace_xe_tlb_inval_fence_send(xe, fence);
-	action[1] = seqno;
-	ret = xe_guc_ct_send(&guc->ct, action, len,
-			     G2H_LEN_DW_TLB_INVALIDATE, 1);
-	if (!ret) {
-		spin_lock_irq(&gt->tlb_inval.pending_lock);
-		/*
-		 * We haven't actually published the TLB fence as per
-		 * pending_fences, but in theory our seqno could have already
-		 * been written as we acquired the pending_lock. In such a case
-		 * we can just go ahead and signal the fence here.
-		 */
-		if (tlb_inval_seqno_past(gt, seqno)) {
-			__inval_fence_signal(xe, fence);
-		} else {
-			fence->inval_time = ktime_get();
-			list_add_tail(&fence->link,
-				      &gt->tlb_inval.pending_fences);
-
-			if (list_is_singular(&gt->tlb_inval.pending_fences))
-				queue_delayed_work(system_wq,
-						   &gt->tlb_inval.fence_tdr,
-						   tlb_timeout_jiffies(gt));
-		}
-		spin_unlock_irq(&gt->tlb_inval.pending_lock);
-	} else {
-		__inval_fence_signal(xe, fence);
-	}
-	if (!ret) {
-		gt->tlb_inval.seqno = (gt->tlb_inval.seqno + 1) %
-			TLB_INVALIDATION_SEQNO_MAX;
-		if (!gt->tlb_inval.seqno)
-			gt->tlb_inval.seqno = 1;
-	}
-	mutex_unlock(&gt->tlb_inval.seqno_lock);
 	xe_gt_stats_incr(gt, XE_GT_STATS_ID_TLB_INVAL, 1);
+	action[1] = fence->seqno;
 
-	return ret;
+	return xe_guc_ct_send(&guc->ct, action, len,
+			      G2H_LEN_DW_TLB_INVALIDATE, 1);
+}
+
+static void xe_tlb_inval_fence_prep(struct xe_tlb_inval_fence *fence)
+{
+	struct xe_tlb_inval *tlb_inval = fence->tlb_inval;
+	struct xe_gt *gt = tlb_inval->private;
+	struct xe_device *xe = gt_to_xe(gt);
+
+	fence->seqno = tlb_inval->seqno;
+	trace_xe_tlb_inval_fence_send(xe, fence);
+
+	spin_lock_irq(&tlb_inval->pending_lock);
+	fence->inval_time = ktime_get();
+	list_add_tail(&fence->link, &tlb_inval->pending_fences);
+
+	if (list_is_singular(&tlb_inval->pending_fences))
+		queue_delayed_work(system_wq,
+				   &tlb_inval->fence_tdr,
+				   tlb_timeout_jiffies(gt));
+	spin_unlock_irq(&tlb_inval->pending_lock);
+
+	tlb_inval->seqno = (tlb_inval->seqno + 1) %
+		TLB_INVALIDATION_SEQNO_MAX;
+	if (!tlb_inval->seqno)
+		tlb_inval->seqno = 1;
 }
 
 #define MAKE_INVAL_OP(type)	((type << XE_GUC_TLB_INVAL_TYPE_SHIFT) | \
@@ -306,7 +291,14 @@ static int xe_tlb_inval_guc(struct xe_gt *gt,
 	};
 	int ret;
 
+	mutex_lock(&gt->tlb_inval.seqno_lock);
+	xe_tlb_inval_fence_prep(fence);
+
 	ret = send_tlb_inval(&gt->uc.guc, fence, action, ARRAY_SIZE(action));
+	if (ret < 0)
+		inval_fence_signal_unlocked(gt_to_xe(gt), fence);
+	mutex_unlock(&gt->tlb_inval.seqno_lock);
+
 	/*
 	 * -ECANCELED indicates the CT is stopped for a GT reset. TLB caches
 	 *  should be nuked on a GT reset so this error can be ignored.
@@ -433,7 +425,7 @@ int xe_tlb_inval_range(struct xe_tlb_inval *tlb_inval,
 #define MAX_TLB_INVALIDATION_LEN	7
 	u32 action[MAX_TLB_INVALIDATION_LEN];
 	u64 length = end - start;
-	int len = 0;
+	int len = 0, ret;
 
 	xe_gt_assert(gt, fence);
 
@@ -494,7 +486,16 @@ int xe_tlb_inval_range(struct xe_tlb_inval *tlb_inval,
 
 	xe_gt_assert(gt, len <= MAX_TLB_INVALIDATION_LEN);
 
-	return send_tlb_inval(&gt->uc.guc, fence, action, len);
+	mutex_lock(&gt->tlb_inval.seqno_lock);
+	xe_tlb_inval_fence_prep(fence);
+
+	ret = send_tlb_inval(&gt->uc.guc, fence, action,
+			     ARRAY_SIZE(action));
+	if (ret < 0)
+		inval_fence_signal_unlocked(xe, fence);
+	mutex_unlock(&gt->tlb_inval.seqno_lock);
+
+	return ret;
 }
 
 /**