Patch "drm/dp_mst: Do not set proposed vcpi directly" has been added to the 5.12-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    drm/dp_mst: Do not set proposed vcpi directly

to the 5.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-dp_mst-do-not-set-proposed-vcpi-directly.patch
and it can be found in the queue-5.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From 35d3e8cb35e75450f87f87e3d314e2d418b6954b Mon Sep 17 00:00:00 2001
From: Wayne Lin <Wayne.Lin at amd.com>
Date: Wed, 16 Jun 2021 11:55:00 +0800
Subject: drm/dp_mst: Do not set proposed vcpi directly

From: Wayne Lin <Wayne.Lin at amd.com>

commit 35d3e8cb35e75450f87f87e3d314e2d418b6954b upstream.

[Why]
When we receive CSN message to notify one port is disconnected, we will
implicitly set its corresponding num_slots to 0. Later on, we will
eventually call drm_dp_update_payload_part1() to arrange down streams.

In drm_dp_update_payload_part1(), we iterate over all proposed_vcpis[]
to do the update. Not specific to a target sink only. For example, if we
light up 2 monitors, Monitor_A and Monitor_B, and then we unplug
Monitor_B. Later on, when we call drm_dp_update_payload_part1() to try
to update payload for Monitor_A, we'll also implicitly clean payload for
Monitor_B at the same time. And finally, when we try to call
drm_dp_update_payload_part1() to clean payload for Monitor_B, we will do
nothing at this time since payload for Monitor_B has been cleaned up
previously.

For StarTech 1to3 DP hub, it seems like if we didn't update DPCD payload
ID table then polling for "ACT Handled"(BIT_1 of DPCD 002C0h) will fail
and this polling will last for 3 seconds.

Therefore, guess the best way is we don't set the proposed_vcpi[]
diretly. Let user of these herlper functions to set the proposed_vcpi
directly.

[How]
1. Revert commit 7617e9621bf2 ("drm/dp_mst: clear time slots for ports
invalid")
2. Tackle the issue in previous commit by skipping those trasient
proposed VCPIs. These stale VCPIs shoulde be explicitly cleared by
user later on.

Changes since v1:
* Change debug macro to use drm_dbg_kms() instead
* Amend the commit message to add Fixed & Cc tags

Signed-off-by: Wayne Lin <Wayne.Lin at amd.com>
Fixes: 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid")
Cc: Lyude Paul <lyude at redhat.com>
Cc: Wayne Lin <Wayne.Lin at amd.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: dri-devel at lists.freedesktop.org
Cc: <stable at vger.kernel.org> # v5.5+
Signed-off-by: Lyude Paul <lyude at redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210616035501.3776-2-Wayne.Lin@amd.com
Reviewed-by: Lyude Paul <lyude at redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |   36 +++++++++-------------------------
 1 file changed, 10 insertions(+), 26 deletions(-)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2499,7 +2499,7 @@ drm_dp_mst_handle_conn_stat(struct drm_d
 {
 	struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
 	struct drm_dp_mst_port *port;
-	int old_ddps, old_input, ret, i;
+	int old_ddps, ret;
 	u8 new_pdt;
 	bool new_mcs;
 	bool dowork = false, create_connector = false;
@@ -2531,7 +2531,6 @@ drm_dp_mst_handle_conn_stat(struct drm_d
 	}
 
 	old_ddps = port->ddps;
-	old_input = port->input;
 	port->input = conn_stat->input_port;
 	port->ldps = conn_stat->legacy_device_plug_status;
 	port->ddps = conn_stat->displayport_device_plug_status;
@@ -2554,28 +2553,6 @@ drm_dp_mst_handle_conn_stat(struct drm_d
 		dowork = false;
 	}
 
-	if (!old_input && old_ddps != port->ddps && !port->ddps) {
-		for (i = 0; i < mgr->max_payloads; i++) {
-			struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i];
-			struct drm_dp_mst_port *port_validated;
-
-			if (!vcpi)
-				continue;
-
-			port_validated =
-				container_of(vcpi, struct drm_dp_mst_port, vcpi);
-			port_validated =
-				drm_dp_mst_topology_get_port_validated(mgr, port_validated);
-			if (!port_validated) {
-				mutex_lock(&mgr->payload_lock);
-				vcpi->num_slots = 0;
-				mutex_unlock(&mgr->payload_lock);
-			} else {
-				drm_dp_mst_topology_put_port(port_validated);
-			}
-		}
-	}
-
 	if (port->connector)
 		drm_modeset_unlock(&mgr->base.lock);
 	else if (create_connector)
@@ -3406,8 +3383,15 @@ int drm_dp_update_payload_part1(struct d
 				port = drm_dp_mst_topology_get_port_validated(
 				    mgr, port);
 				if (!port) {
-					mutex_unlock(&mgr->payload_lock);
-					return -EINVAL;
+					if (vcpi->num_slots == payload->num_slots) {
+						cur_slots += vcpi->num_slots;
+						payload->start_slot = req_payload.start_slot;
+						continue;
+					} else {
+						drm_dbg_kms("Fail:set payload to invalid sink");
+						mutex_unlock(&mgr->payload_lock);
+						return -EINVAL;
+					}
 				}
 				put_port = true;
 			}


Patches currently in stable-queue which might be from Wayne.Lin at amd.com are

queue-5.12/drm-dp_mst-do-not-set-proposed-vcpi-directly.patch