Mesa (master): panfrost: Avoid integer underflow in rt_count_1

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Module: Mesa
Branch: master
Commit: 9addb82148c487d6660aecea1af370c2d21d1788
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=9addb82148c487d6660aecea1af370c2d21d1788

Author: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Date:   Tue Jul 14 17:08:54 2020 -0400

panfrost: Avoid integer underflow in rt_count_1

If rt_count = 0, this underflows to MAX_MRT. The hw doesn't seem to care
but it's semantically incorrect and confuses pandecode.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5858>

---

 src/gallium/drivers/panfrost/pan_mfbd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gallium/drivers/panfrost/pan_mfbd.c b/src/gallium/drivers/panfrost/pan_mfbd.c
index ac890b5c56f..7e9d8cb013a 100644
--- a/src/gallium/drivers/panfrost/pan_mfbd.c
+++ b/src/gallium/drivers/panfrost/pan_mfbd.c
@@ -482,7 +482,7 @@ panfrost_emit_mfbd(struct panfrost_batch *batch, unsigned vertex_count)
                 /* Seems to configure tib size */
                 .unk1 = pan_is_large_tib(batch) ? 0xc80 : 0x1080,
 
-                .rt_count_1 = MALI_POSITIVE(batch->key.nr_cbufs),
+                .rt_count_1 = MALI_POSITIVE(MAX2(batch->key.nr_cbufs, 1)),
                 .rt_count_2 = 4,
         };