linux-kernel - [PATCH 5.10 013/104] drm/dp_mst: Dont report ports connected if nothing is attached to them

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Date:   Mon, 15 Feb 2021 16:26:26 +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, Wayne Lin <Wayne.Lin@....com>,
        Lyude Paul <lyude@...hat.com>, intel-gfx@...ts.freedesktop.org,
        Imre Deak <imre.deak@...el.com>,
        Thiago Macieira <gitlab@...lab.freedesktop.org>
Subject: [PATCH 5.10 013/104] drm/dp_mst: Dont report ports connected if nothing is attached to them

From: Imre Deak <imre.deak@...el.com>

commit 873e5bb9fbd99e4a26c448b5c7af942a6d7aa60d upstream.

Reporting a port as connected if nothing is attached to them leads to
any i2c transactions on this port trying to use an uninitialized i2c
adapter, fix this.

Let's account for this case even if branch devices have no good reason
to report a port as plugged with their peer device type set to 'none'.

Fixes: db1a07956968 ("drm/dp_mst: Handle SST-only branch device case")
Cc: Wayne Lin <Wayne.Lin@....com>
Cc: Lyude Paul <lyude@...hat.com>
Cc: <stable@...r.kernel.org> # v5.5+
Cc: intel-gfx@...ts.freedesktop.org
Signed-off-by: Imre Deak <imre.deak@...el.com>
Reviewed-by: Lyude Paul <lyude@...hat.com>
Reported-by: Thiago Macieira <gitlab@...lab.freedesktop.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210201120145.350258-1-imre.deak@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/drm_dp_mst_topology.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4224,6 +4224,7 @@ drm_dp_mst_detect_port(struct drm_connec
 
 	switch (port->pdt) {
 	case DP_PEER_DEVICE_NONE:
+		break;
 	case DP_PEER_DEVICE_MST_BRANCHING:
 		if (!port->mcs)
 			ret = connector_status_connected;