drm/amd/display: Fix potential integer wraparound resulting in a hang

[Why] If VUPDATE_END is before VUPDATE_START the delay calculated can become very large, causing a soft hang. [How] Take the absolute value of the difference between START and END. Signed-off-by: Aric Cyr <[email protected]> Reviewed-by: Nicholas Kazlauskas <[email protected]> Acked-by: Qingqing Zhuo <[email protected]> Signed-off-by: Alex Deucher <[email protected]> Cc: [email protected]
josf · May 27, 2020 · 4e51832 · 4e51832
1 parent f7d5991
commit 4e51832
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
@@ -1684,6 +1684,8 @@ static void delay_cursor_until_vupdate(struct dc *dc, struct pipe_ctx *pipe_ctx)
 		return;
 
 	/* Stall out until the cursor update completes. */
+	if (vupdate_end < vupdate_start)
+		vupdate_end += stream->timing.v_total;
 	us_vupdate = (vupdate_end - vupdate_start + 1) * us_per_line;
 	udelay(us_to_vupdate + us_vupdate);
 }