[PATCH 01/31] drm/amd/display: Avoid MPC infinite loop

[Alex Hung]

From: Aric Cyr <aric.cyr at amd.com>

[why]
In some cases MPC tree bottom pipe ends up point to itself.  This causes
iterating from top to bottom to hang the system in an infinite loop.

[how]
When looping to next MPC bottom pipe, check that the pointer is not same
as current to avoid infinite loop.

Reviewed-by: Josip Pavic <Josip.Pavic at amd.com>
Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Acked-by: Alex Hung <alex.hung at amd.com>
Signed-off-by: Aric Cyr <aric.cyr at amd.com>
---
 drivers/gpu/drm/amd/display/dc/dcn10/dcn10_mpc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_mpc.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_mpc.c
index 11019c2c62cc..769974375b4b 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_mpc.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_mpc.c
@@ -49,6 +49,11 @@ void mpc1_set_bg_color(struct mpc *mpc,
 
 	/* find bottommost mpcc. */
 	while (bottommost_mpcc->mpcc_bot) {
+		/* avoid circular linked link */
+		ASSERT(bottommost_mpcc != bottommost_mpcc->mpcc_bot);
+		if (bottommost_mpcc == bottommost_mpcc->mpcc_bot)
+			break;
+
 		bottommost_mpcc = bottommost_mpcc->mpcc_bot;
 	}
 
-- 
2.37.1