[RFC PATCH v2 2/6] drm/gma500: do not underflow an unpinned GEM object

[Gabriel Gama <operatingsystemsdepression@gmail.com>]

Return after warning if psb_gem_unpin() is called without a pin.
Decrementing zero makes in_gart negative, so later pins incorrectly skip
backing-page and mapping setup. Release the reservation lock normally.

Signed-off-by: Gabriel Gama <operatingsystemsdepression@gmail.com>
---
 drivers/gpu/drm/gma500/gem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/gem.c b/drivers/gpu/drm/gma500/gem.c
index 7250bf660..fa5d3f137 100644
--- a/drivers/gpu/drm/gma500/gem.c
+++ b/drivers/gpu/drm/gma500/gem.c
@@ -85,7 +85,8 @@ void psb_gem_unpin(struct psb_gem_object *pobj)
 	if (drm_WARN_ONCE(dev, ret, "dma_resv_lock() failed, ret=%d\n", ret))
 		return;
 
-	WARN_ON(!pobj->in_gart);
+	if (WARN_ON(!pobj->in_gart))
+		goto out;
 
 	--pobj->in_gart;