linux-kernel - [PATCH 5.4 090/434] drm/amd/display: Set number of pipes to 1 if the second pipe was disabled

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Date:   Sun, 29 Dec 2019 18:22:23 +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, Nikola Cornij <nikola.cornij@....com>,
        Dmytro Laktyushkin <Dmytro.Laktyushkin@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 090/434] drm/amd/display: Set number of pipes to 1 if the second pipe was disabled

From: Nikola Cornij <nikola.cornij@....com>

[ Upstream commit 2fef0faa1cdc5d41ce3ef83f7b8f7e7ecb02d700 ]

[why]
Some ODM-related register settings are inconsistently updated by VBIOS, causing
the state in DC to be invalid, which would then end up crashing in certain
use-cases (such as disable/enable device).

[how]
Check the enabled status of the second pipe when determining the number of
OPTC sources. If the second pipe is disabled, set the number of sources to 1
regardless of other settings (that may not be updated correctly).

Signed-off-by: Nikola Cornij <nikola.cornij@....com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@....com>
Acked-by: Leo Li <sunpeng.li@....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_optc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_optc.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_optc.c
index 2137e2be2140..dda90995ba93 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_optc.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_optc.c
@@ -287,6 +287,10 @@ void optc2_get_optc_source(struct timing_generator *optc,
 		*num_of_src_opp = 2;
 	else
 		*num_of_src_opp = 1;
+
+	/* Work around VBIOS not updating OPTC_NUM_OF_INPUT_SEGMENT */
+	if (*src_opp_id_1 == 0xf)
+		*num_of_src_opp = 1;
 }
 
 void optc2_set_dwb_source(struct timing_generator *optc,
-- 
2.20.1