[PATCH 14/20] drm/amd/display: Add Overflow check to skip MALL

[Stylon Wang]

From: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>

[Why]
In some small modes (<200pixels) the stutter period is really big and will cause
overflow. In these cases we shouldnt try to enable MALL as it will exceeds range
of hysteresis timer (this can be seen in some IGT tests where the
plane size is small)

[How]
Compare the stutter_period with the frame time and if we will overflow
there is no point in trying to enable MALL (and see the ASSERT) so we
early exist in this case

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Acked-by: Stylon Wang <stylon.wang at amd.com>
---
 drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c
index d53f8b39699b..83685310a391 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c
@@ -813,6 +813,15 @@ bool dcn30_apply_idle_power_optimizations(struct dc *dc, bool enable)
 						(100LL + dc->debug.mall_additional_timer_percent) + denom - 1),
 						denom) - 64LL;
 
+				/* In some cases the stutter period is really big (tiny modes) in these
+				 * cases MALL cant be enabled, So skip these cases to avoid a ASSERT()
+				 *
+				 * We can check if stutter_period is more than 1/10th the frame time to
+				 * consider if we can actually meet the range of hysteresis timer
+				 */
+				if (stutter_period > 100000/refresh_hz)
+					return false;
+
 				/* scale should be increased until it fits into 6 bits */
 				while (tmr_delay & ~0x3F) {
 					tmr_scale++;
-- 
2.25.1