linux-kernel - [PATCH AUTOSEL 6.4 18/31] drm/amd/display: Use DTBCLK as refclk instead of DPREFCLK

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Message-Id: <20230908193201.3462957-18-sashal@kernel.org>
Date:   Fri,  8 Sep 2023 15:31:47 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Austin Zheng <austin.zheng@....com>,
        Alvin Lee <alvin.lee2@....com>,
        Tom Chung <chiahsuan.chung@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, harry.wentland@....com,
        sunpeng.li@....com, Rodrigo.Siqueira@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, qingqing.zhuo@....com, Syed.Hassan@....com,
        syedsaaem.rizvi@....com, hersenxs.wu@....com,
        jiapeng.chong@...ux.alibaba.com, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.4 18/31] drm/amd/display: Use DTBCLK as refclk instead of DPREFCLK

From: Austin Zheng <austin.zheng@....com>

[ Upstream commit 4a30cc2bd281fa176a68b5305cd3695d636152ad ]

[Why]
Flash of corruption observed when UCLK switching after transitioning
from DTBCLK to DPREFCLK on subVP(DP) + subVP(HDMI) config
Scenario where DPREFCLK is required instead of DTBCLK is not expected

[How]
Always set the DTBCLK source as DTBCLK0

Reviewed-by: Alvin Lee <alvin.lee2@....com>
Acked-by: Tom Chung <chiahsuan.chung@....com>
Signed-off-by: Austin Zheng <austin.zheng@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c
index ffbb739d85b69..8496ff4a25e35 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c
@@ -290,7 +290,8 @@ static void dccg32_set_dpstreamclk(
 	struct dcn_dccg *dccg_dcn = TO_DCN_DCCG(dccg);
 
 	/* set the dtbclk_p source */
-	dccg32_set_dtbclk_p_src(dccg, src, otg_inst);
+	/* always program refclk as DTBCLK. No use-case expected to require DPREFCLK as refclk */
+	dccg32_set_dtbclk_p_src(dccg, DTBCLK0, otg_inst);
 
 	/* enabled to select one of the DTBCLKs for pipe */
 	switch (dp_hpo_inst) {
-- 
2.40.1