linux-kernel - [PATCH 5.2 064/144] drm/amd/display: No audio endpoint for Dell MST display

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Message-Id: <20190814165802.514981594@linuxfoundation.org>
Date:   Wed, 14 Aug 2019 19:00:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Harmanprit Tatla <harmanprit.tatla@....com>,
        Aric Cyr <aric.cyr@....com>, Anthony Koo <Anthony.Koo@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.2 064/144] drm/amd/display: No audio endpoint for Dell MST display

[ Upstream commit 5b25e5f1a97284020abee7348427f89abdb674e8 ]

[Why]
There are certain MST displays (i.e. Dell P2715Q)
that although have the MST feature set to off may still
report it is a branch device and a non-zero
value for downstream port present.
This can lead to us incorrectly classifying a
dp dongle connection as being active and
disabling the audio endpoint for the display.

[How]
Modified the placement and
condition used to assign
the is_branch_dev bit.

Signed-off-by: Harmanprit Tatla <harmanprit.tatla@....com>
Reviewed-by: Aric Cyr <aric.cyr@....com>
Acked-by: Anthony Koo <Anthony.Koo@....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/core/dc_link_dp.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 253311864cdd5..966aa3b754c5b 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -2218,11 +2218,18 @@ static void get_active_converter_info(
 		link->dpcd_caps.dongle_type = DISPLAY_DONGLE_NONE;
 		ddc_service_set_dongle_type(link->ddc,
 				link->dpcd_caps.dongle_type);
+		link->dpcd_caps.is_branch_dev = false;
 		return;
 	}
 
 	/* DPCD 0x5 bit 0 = 1, it indicate it's branch device */
-	link->dpcd_caps.is_branch_dev = ds_port.fields.PORT_PRESENT;
+	if (ds_port.fields.PORT_TYPE == DOWNSTREAM_DP) {
+		link->dpcd_caps.is_branch_dev = false;
+	}
+
+	else {
+		link->dpcd_caps.is_branch_dev = ds_port.fields.PORT_PRESENT;
+	}
 
 	switch (ds_port.fields.PORT_TYPE) {
 	case DOWNSTREAM_VGA:
-- 
2.20.1