[PATCH v2 0/2] Fix observed mst problems with StarTech hub

[PATCH v2 0/2] Fix observed mst problems with StarTech hub

[Wayne Lin]

Use Startech 1to3 DP hub to do some mst hotplug tests and find some
light up issues.

1. ACT polling timeout:
   Which is due to we didn't update DPCD payload table but still try
   to send ACT and polling for "ACT Handled" bit
2. Not all monitors light up:
   Due to we wrongly set unavailable VCP ID for new streams

Changes since v1:
* Add appropriate tags: Fixes & Cc
* Change debug macro to use drm_dbg_kms() instead

Wayne Lin (2):
  drm/dp_mst: Do not set proposed vcpi directly
  drm/dp_mst: Avoid to mess up payload table by ports in stale topology

 drivers/gpu/drm/drm_dp_mst_topology.c | 65 ++++++++++++++++-----------
 1 file changed, 39 insertions(+), 26 deletions(-)

-- 
2.17.1

[PATCH v2 1/2] drm/dp_mst: Do not set proposed vcpi directly

[Wayne Lin]

[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@amd.com>
Fixes: 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid")
Cc: Lyude Paul <lyude@redhat.com>
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.5+
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 36 ++++++++-------------------
 1 file changed, 10 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 32b7f8983b94..b41b837db66d 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2501,7 +2501,7 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
 {
 	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;
@@ -2533,7 +2533,6 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
 	}
 
 	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;
@@ -2555,28 +2554,6 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
 		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)
@@ -3410,8 +3387,15 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
 				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;
 			}
-- 
2.17.1

Re: [PATCH v2 1/2] drm/dp_mst: Do not set proposed vcpi directly

[Harry Wentland]

On 2021-06-15 11:55 p.m., Wayne Lin wrote:
> [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@amd.com>
> Fixes: 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid")
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Wayne Lin <Wayne.Lin@amd.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: dri-devel@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v5.5+
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 36 ++++++++-------------------
>  1 file changed, 10 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 32b7f8983b94..b41b837db66d 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -2501,7 +2501,7 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
>  {
>  	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;
> @@ -2533,7 +2533,6 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
>  	}
>  
>  	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;
> @@ -2555,28 +2554,6 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
>  		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)
> @@ -3410,8 +3387,15 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
>  				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");

drm_dbg_kms takes a drm_device as first parameter.

Harry

> +						mutex_unlock(&mgr->payload_lock);
> +						return -EINVAL;
> +					}
>  				}
>  				put_port = true;
>  			}
> 

Re: [PATCH v2 1/2] drm/dp_mst: Do not set proposed vcpi directly

[Lin, Wayne]

[AMD Official Use Only]

________________________________________
> From: Wentland, Harry <Harry.Wentland@amd.com>
> Sent: Thursday, June 17, 2021 03:53
> To: Lin, Wayne; dri-devel@lists.freedesktop.org
> Cc: lyude@redhat.com; Kazlauskas, Nicholas; Zuo, Jerry; Pillai, Aurabindo; Maarten Lankhorst; Maxime Ripard; Thomas Zimmermann; stable@vger.kernel.org
> Subject: Re: [PATCH v2 1/2] drm/dp_mst: Do not set proposed vcpi directly
>
>
>
> On 2021-06-15 11:55 p.m., Wayne Lin wrote:
> > [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@amd.com>
> > Fixes: 7617e9621bf2 ("drm/dp_mst: clear time slots for ports invalid")
> > Cc: Lyude Paul <lyude@redhat.com>
> > Cc: Wayne Lin <Wayne.Lin@amd.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: Thomas Zimmermann <tzimmermann@suse.de>
> > Cc: dri-devel@lists.freedesktop.org
> > Cc: <stable@vger.kernel.org> # v5.5+
> > ---
> >  drivers/gpu/drm/drm_dp_mst_topology.c | 36 ++++++++-------------------
> >  1 file changed, 10 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index 32b7f8983b94..b41b837db66d 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -2501,7 +2501,7 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
> >  {
> >       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;
> > @@ -2533,7 +2533,6 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
> >       }
> >
> >       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;
> > @@ -2555,28 +2554,6 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb,
> >               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)
> > @@ -3410,8 +3387,15 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
> >                               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");
>
> drm_dbg_kms takes a drm_device as first parameter.
>
> Harry

Thanks Harry. Should be addressed by another patch provided by José.
>
> > +                                             mutex_unlock(&mgr->payload_lock);
> > +                                             return -EINVAL;
> > +                                     }
> >                               }
> >                               put_port = true;
> >                       }
> >
--
Regards,
Wayne

[PATCH v2 2/2] drm/dp_mst: Avoid to mess up payload table by ports in stale topology

[Wayne Lin]

[Why]
After unplug/hotplug hub from the system, userspace might start to
clear stale payloads gradually. If we call drm_dp_mst_deallocate_vcpi()
to release stale VCPI of those ports which are not relating to current
topology, we have chane to wrongly clear active payload table entry for
current topology.

E.g.
We have allocated VCPI 1 in current payload table and we call
drm_dp_mst_deallocate_vcpi() to clean VCPI 1 in stale topology. In
drm_dp_mst_deallocate_vcpi(), it will call drm_dp_mst_put_payload_id()
tp put VCPI 1 and which means ID 1 is available again. Thereafter, if we
want to allocate a new payload stream, it will find ID 1 is available by
drm_dp_mst_assign_payload_id(). However, ID 1 is being used

[How]
Check target sink is relating to current topology or not before doing
any payload table update.
Searching upward to find the target sink's relevant root branch device.
If the found root branch device is not the same root of current
topology, don't update payload table.

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

Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 29 +++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index b41b837db66d..9ac148efd9e4 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -94,6 +94,9 @@ static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port);
 static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_mst_port *port);
 static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr);
 
+static bool drm_dp_mst_port_downstream_of_branch(struct drm_dp_mst_port *port,
+						 struct drm_dp_mst_branch *branch);
+
 #define DBG_PREFIX "[dp_mst]"
 
 #define DP_STR(x) [DP_ ## x] = #x
@@ -3366,6 +3369,7 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
 	struct drm_dp_mst_port *port;
 	int i, j;
 	int cur_slots = 1;
+	bool skip;
 
 	mutex_lock(&mgr->payload_lock);
 	for (i = 0; i < mgr->max_payloads; i++) {
@@ -3380,6 +3384,14 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
 			port = container_of(vcpi, struct drm_dp_mst_port,
 					    vcpi);
 
+			mutex_lock(&mgr->lock);
+			skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
+			mutex_unlock(&mgr->lock);
+
+			if (skip) {
+				drm_dbg_kms("Virtual channel %d is not in current topology\n", i);
+				continue;
+			}
 			/* Validated ports don't matter if we're releasing
 			 * VCPI
 			 */
@@ -3479,6 +3491,7 @@ int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
 	struct drm_dp_mst_port *port;
 	int i;
 	int ret = 0;
+	bool skip;
 
 	mutex_lock(&mgr->payload_lock);
 	for (i = 0; i < mgr->max_payloads; i++) {
@@ -3488,6 +3501,13 @@ int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
 
 		port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
 
+		mutex_lock(&mgr->lock);
+		skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
+		mutex_unlock(&mgr->lock);
+
+		if (skip)
+			continue;
+
 		drm_dbg_kms(mgr->dev, "payload %d %d\n", i, mgr->payloads[i].payload_state);
 		if (mgr->payloads[i].payload_state == DP_PAYLOAD_LOCAL) {
 			ret = drm_dp_create_payload_step2(mgr, port, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
@@ -4574,9 +4594,18 @@ EXPORT_SYMBOL(drm_dp_mst_reset_vcpi_slots);
 void drm_dp_mst_deallocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 				struct drm_dp_mst_port *port)
 {
+	bool skip;
+
 	if (!port->vcpi.vcpi)
 		return;
 
+	mutex_lock(&mgr->lock);
+	skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
+	mutex_unlock(&mgr->lock);
+
+	if (skip)
+		return;
+
 	drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
 	port->vcpi.num_slots = 0;
 	port->vcpi.pbn = 0;
-- 
2.17.1

Re: [PATCH v2 2/2] drm/dp_mst: Avoid to mess up payload table by ports in stale topology

[Souza, Jose]

On Wed, 2021-06-16 at 11:55 +0800, Wayne Lin wrote:
> [Why]
> After unplug/hotplug hub from the system, userspace might start to
> clear stale payloads gradually. If we call drm_dp_mst_deallocate_vcpi()
> to release stale VCPI of those ports which are not relating to current
> topology, we have chane to wrongly clear active payload table entry for
> current topology.
> 
> E.g.
> We have allocated VCPI 1 in current payload table and we call
> drm_dp_mst_deallocate_vcpi() to clean VCPI 1 in stale topology. In
> drm_dp_mst_deallocate_vcpi(), it will call drm_dp_mst_put_payload_id()
> tp put VCPI 1 and which means ID 1 is available again. Thereafter, if we
> want to allocate a new payload stream, it will find ID 1 is available by
> drm_dp_mst_assign_payload_id(). However, ID 1 is being used
> 
> [How]
> Check target sink is relating to current topology or not before doing
> any payload table update.
> Searching upward to find the target sink's relevant root branch device.
> If the found root branch device is not the same root of current
> topology, don't update payload table.
> 
> Changes since v1:
> * Change debug macro to use drm_dbg_kms() instead
> * Amend the commit message to add Cc tag.
> 
> Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
> Cc: stable@vger.kernel.org
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 29 +++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index b41b837db66d..9ac148efd9e4 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -94,6 +94,9 @@ static int drm_dp_mst_register_i2c_bus(struct drm_dp_mst_port *port);
>  static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_mst_port *port);
>  static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr);
>  
> +static bool drm_dp_mst_port_downstream_of_branch(struct drm_dp_mst_port *port,
> +						 struct drm_dp_mst_branch *branch);
> +
>  #define DBG_PREFIX "[dp_mst]"
>  
>  #define DP_STR(x) [DP_ ## x] = #x
> @@ -3366,6 +3369,7 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
>  	struct drm_dp_mst_port *port;
>  	int i, j;
>  	int cur_slots = 1;
> +	bool skip;
>  
>  	mutex_lock(&mgr->payload_lock);
>  	for (i = 0; i < mgr->max_payloads; i++) {
> @@ -3380,6 +3384,14 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
>  			port = container_of(vcpi, struct drm_dp_mst_port,
>  					    vcpi);
>  
> +			mutex_lock(&mgr->lock);
> +			skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
> +			mutex_unlock(&mgr->lock);
> +
> +			if (skip) {
> +				drm_dbg_kms("Virtual channel %d is not in current topology\n", i);

Missing dev/drm parameter and breaking the build.

> +				continue;
> +			}
>  			/* Validated ports don't matter if we're releasing
>  			 * VCPI
>  			 */
> @@ -3479,6 +3491,7 @@ int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
>  	struct drm_dp_mst_port *port;
>  	int i;
>  	int ret = 0;
> +	bool skip;
>  
>  	mutex_lock(&mgr->payload_lock);
>  	for (i = 0; i < mgr->max_payloads; i++) {
> @@ -3488,6 +3501,13 @@ int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
>  
>  		port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
>  
> +		mutex_lock(&mgr->lock);
> +		skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
> +		mutex_unlock(&mgr->lock);
> +
> +		if (skip)
> +			continue;
> +
>  		drm_dbg_kms(mgr->dev, "payload %d %d\n", i, mgr->payloads[i].payload_state);
>  		if (mgr->payloads[i].payload_state == DP_PAYLOAD_LOCAL) {
>  			ret = drm_dp_create_payload_step2(mgr, port, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
> @@ -4574,9 +4594,18 @@ EXPORT_SYMBOL(drm_dp_mst_reset_vcpi_slots);
>  void drm_dp_mst_deallocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
>  				struct drm_dp_mst_port *port)
>  {
> +	bool skip;
> +
>  	if (!port->vcpi.vcpi)
>  		return;
>  
> +	mutex_lock(&mgr->lock);
> +	skip = !drm_dp_mst_port_downstream_of_branch(port, mgr->mst_primary);
> +	mutex_unlock(&mgr->lock);
> +
> +	if (skip)
> +		return;
> +
>  	drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
>  	port->vcpi.num_slots = 0;
>  	port->vcpi.pbn = 0;