linux-kernel - [PATCH 5.4 052/434] drm/amd/display: OTC underflow fix

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Date:   Sun, 29 Dec 2019 18:21:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jaehyun Chung <jaehyun.chung@....com>,
        Alvin Lee <Alvin.Lee2@....com>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 052/434] drm/amd/display: OTC underflow fix

From: Jaehyun Chung <jaehyun.chung@....com>

[ Upstream commit 785908cf19c9eb4803f6bf9c0a7447dc3661d5c3 ]

[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@....com>
Reviewed-by: Alvin Lee <Alvin.Lee2@....com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 6b2f2f1a1c9c..3980c7b78259 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c
@@ -1765,7 +1765,7 @@ int dcn20_populate_dml_pipes_from_context(
 			pipe_cnt = i;
 			continue;
 		}
-		if (!resource_are_streams_timing_synchronizable(
+		if (dc->debug.disable_timing_sync || !resource_are_streams_timing_synchronizable(
 				res_ctx->pipe_ctx[pipe_cnt].stream,
 				res_ctx->pipe_ctx[i].stream)) {
 			synchronized_vblank = false;
-- 
2.20.1