Re: [PATCH v5 3/3] drm_dp_cec: add MST support

[Lyude Paul <lyude@redhat.com>]

On Tue, 2021-05-25 at 10:59 +1000, Sam McNally wrote:
> With DP v2.0 errata E5, CEC tunneling can be supported through an MST
> topology.
> 
> When tunneling CEC through an MST port, CEC IRQs are delivered via a
> sink event notify message; when a sink event notify message is received,
> trigger CEC IRQ handling - ESI1 is not used for remote CEC IRQs so its
> value is not checked.
> 
> Register and unregister for all MST connectors, ensuring their
> drm_dp_aux_cec struct won't be accessed uninitialized.
> 
> Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Signed-off-by: Sam McNally <sammc@chromium.org>
> ---
> 
> (no changes since v4)
> 
> Changes in v4:
> - Removed use of work queues
> - Updated checks of aux.transfer to accept aux.is_remote
> 
> Changes in v3:
> - Fixed whitespace in drm_dp_cec_mst_irq_work()
> - Moved drm_dp_cec_mst_set_edid_work() with the other set_edid functions
> 
> Changes in v2:
> - Used aux->is_remote instead of aux->cec.is_mst, removing the need for
>   the previous patch in the series
> - Added a defensive check for null edid in the deferred set_edid work,
>   in case the edid is no longer valid at that point
> 
>  drivers/gpu/drm/drm_dp_cec.c          | 20 ++++++++++++++++----
>  drivers/gpu/drm/drm_dp_mst_topology.c | 24 ++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
> index 3ab2609f9ec7..1abd3f4654dc 100644
> --- a/drivers/gpu/drm/drm_dp_cec.c
> +++ b/drivers/gpu/drm/drm_dp_cec.c
> @@ -14,6 +14,7 @@
>  #include <drm/drm_connector.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_dp_helper.h>
> +#include <drm/drm_dp_mst_helper.h>
>  
>  /*
>   * Unfortunately it turns out that we have a chicken-and-egg situation
> @@ -245,13 +246,22 @@ void drm_dp_cec_irq(struct drm_dp_aux *aux)
>         int ret;
>  
>         /* No transfer function was set, so not a DP connector */
> -       if (!aux->transfer)
> +       if (!aux->transfer && !aux->is_remote)
>                 return;
>  
>         mutex_lock(&aux->cec.lock);
>         if (!aux->cec.adap)
>                 goto unlock;
>  
> +       if (aux->is_remote) {
> +               /*
> +                * For remote connectors, CEC IRQ is triggered by an
> explicit
> +                * message so ESI1 is not involved.
> +                */
> +               drm_dp_cec_handle_irq(aux);
> +               goto unlock;
> +       }
> +
>         ret = drm_dp_dpcd_readb(aux, DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,
>                                 &cec_irq);
>         if (ret < 0 || !(cec_irq & DP_CEC_IRQ))
> @@ -307,7 +317,7 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const
> struct edid *edid)
>         u8 cap;
>  
>         /* No transfer function was set, so not a DP connector */
> -       if (!aux->transfer)
> +       if (!aux->transfer && !aux->is_remote)
>                 return;
>  
>  #ifndef CONFIG_MEDIA_CEC_RC
> @@ -375,6 +385,7 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const
> struct edid *edid)
>  unlock:
>         mutex_unlock(&aux->cec.lock);
>  }
> +
>  EXPORT_SYMBOL(drm_dp_cec_set_edid);

probably want to get rid of this whitespace

With that fixed, this is:

Reviewed-by: Lyude Paul <lyude@redhat.com>

>  
>  /*
> @@ -383,7 +394,7 @@ EXPORT_SYMBOL(drm_dp_cec_set_edid);
>  void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)
>  {
>         /* No transfer function was set, so not a DP connector */
> -       if (!aux->transfer)
> +       if (!aux->transfer && !aux->is_remote)
>                 return;
>  
>         cancel_delayed_work_sync(&aux->cec.unregister_work);
> @@ -393,6 +404,7 @@ void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)
>                 goto unlock;
>  
>         cec_phys_addr_invalidate(aux->cec.adap);
> +
>         /*
>          * We're done if we want to keep the CEC device
>          * (drm_dp_cec_unregister_delay is >= NEVER_UNREG_DELAY) or if the
> @@ -428,7 +440,7 @@ void drm_dp_cec_register_connector(struct drm_dp_aux
> *aux,
>                                    struct drm_connector *connector)
>  {
>         WARN_ON(aux->cec.adap);
> -       if (WARN_ON(!aux->transfer))
> +       if (WARN_ON(!aux->transfer && !aux->is_remote))
>                 return;
>         aux->cec.connector = connector;
>         INIT_DELAYED_WORK(&aux->cec.unregister_work,
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 29aad3b6b31a..5612caf9fb49 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -2359,6 +2359,8 @@ static void build_mst_prop_path(const struct
> drm_dp_mst_branch *mstb,
>  int drm_dp_mst_connector_late_register(struct drm_connector *connector,
>                                        struct drm_dp_mst_port *port)
>  {
> +       drm_dp_cec_register_connector(&port->aux, connector);
> +
>         drm_dbg_kms(port->mgr->dev, "registering %s remote bus for %s\n",
>                     port->aux.name, connector->kdev->kobj.name);
>  
> @@ -2382,6 +2384,8 @@ void drm_dp_mst_connector_early_unregister(struct
> drm_connector *connector,
>         drm_dbg_kms(port->mgr->dev, "unregistering %s remote bus for %s\n",
>                     port->aux.name, connector->kdev->kobj.name);
>         drm_dp_aux_unregister_devnode(&port->aux);
> +
> +       drm_dp_cec_unregister_connector(&port->aux);
>  }
>  EXPORT_SYMBOL(drm_dp_mst_connector_early_unregister);
>  
> @@ -2682,6 +2686,21 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch
> *mstb,
>                 queue_work(system_long_wq, &mstb->mgr->work);
>  }
>  
> +static void
> +drm_dp_mst_handle_sink_event(struct drm_dp_mst_branch *mstb,
> +                           struct drm_dp_sink_event_notify *sink_event)
> +{
> +       struct drm_dp_mst_port *port;
> +
> +       if (sink_event->event_id & DP_SINK_EVENT_CEC_IRQ_EVENT) {
> +               port = drm_dp_get_port(mstb, sink_event->port_number);
> +               if (port) {
> +                       drm_dp_cec_irq(&port->aux);
> +                       drm_dp_mst_topology_put_port(port);
> +               }
> +       }
> +}
> +
>  static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct
> drm_dp_mst_topology_mgr *mgr,
>                                                                u8 lct, u8
> *rad)
>  {
> @@ -4170,6 +4189,8 @@ drm_dp_mst_process_up_req(struct
> drm_dp_mst_topology_mgr *mgr,
>         if (msg->req_type == DP_CONNECTION_STATUS_NOTIFY) {
>                 drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat);
>                 hotplug = true;
> +       } else if (msg->req_type == DP_SINK_EVENT_NOTIFY) {
> +               drm_dp_mst_handle_sink_event(mstb, &msg->u.sink_event);
>         }
>  
>         drm_dp_mst_topology_put_mstb(mstb);
> @@ -4362,6 +4383,8 @@ drm_dp_mst_detect_port(struct drm_connector
> *connector,
>                 break;
>         }
>  out:
> +       if (ret != connector_status_connected)
> +               drm_dp_cec_unset_edid(&port->aux);
>         drm_dp_mst_topology_put_port(port);
>         return ret;
>  }
> @@ -4392,6 +4415,7 @@ struct edid *drm_dp_mst_get_edid(struct drm_connector
> *connector, struct drm_dp_
>                 edid = drm_get_edid(connector, &port->aux.ddc);
>         }
>         port->has_audio = drm_detect_monitor_audio(edid);
> +       drm_dp_cec_set_edid(&port->aux, edid);
>         drm_dp_mst_topology_put_port(port);
>         return edid;
>  }

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat