drm/msm/mdp5: Fix negative SMP block allocation

In case we request a number of SMP blocks which is lower than
the already reserved blocks, we should not try to allocate a
negative number, but 0 blocks instead.

Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_smp.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_smp.c
index bf551885e019..1f795af89680 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) {