[PATCH 13/17] drm/amd/display: OTC underflow fix

Bhawanpreet Lakha Bhawanpreet.Lakha at amd.com
Wed Aug 28 21:03:50 UTC 2019

From: Jaehyun Chung <jaehyun.chung at amd.com>

[Why] Underflow occurs on some display setups(repro'd on 3x4K HDR) on boot,
mode set, and hot-plugs with. Underflow occurs because mem clk
is not set high after disabling pstate switching. This behaviour occurs
because some calculations assumed displays were synchronized.

[How] Add a condition to check if timing sync is disabled so that
synchronized vblank can be set to false.

Signed-off-by: Jaehyun Chung <jaehyun.chung at amd.com>
Reviewed-by: Alvin Lee <Alvin.Lee2 at amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
 drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
index 353e3e7cb929..62e9a9826c97 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
@@ -1757,7 +1757,7 @@ int dcn20_populate_dml_pipes_from_context(
 			pipe_cnt = i;
-		if (!resource_are_streams_timing_synchronizable(
+		if (dc->debug.disable_timing_sync || !resource_are_streams_timing_synchronizable(
 				res_ctx->pipe_ctx[i].stream)) {
 			synchronized_vblank = false;

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