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

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[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 <aric.cyr@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Aric Cyr 2020-05-12 11:48:48 -04:00 committed by Alex Deucher
parent f7d5991b92
commit 4e5183200d
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
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@ -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);
}