diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_smp.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_smp.c
index bf551885e0197ed7421f32ab8976b66580e41dd5..1f795af89680103211878ac48f77d506981395a6 100644
--- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_smp.c
+++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_smp.c
@@ -119,9 +119,10 @@ static int smp_request_block(struct mdp5_smp *smp,
 
 	spin_lock_irqsave(&smp->state_lock, flags);
 
-	nblks -= reserved;
-	if (reserved)
+	if (reserved) {
+		nblks = max(0, nblks - reserved);
 		DBG("%d MMBs allocated (%d reserved)", nblks, reserved);
+	}
 
 	avail = cnt - bitmap_weight(smp->state, cnt);
 	if (nblks > avail) {