[PATCH v8 10/39] drm/display: hdmi-state-helper: Sync SCDC state on hotplug

[Cristian Ciocaltea]

Hi Maxime,

On 7/7/26 2:31 PM, Maxime Ripard wrote:
> Hi,
> 
> On Thu, Jul 02, 2026 at 05:46:23PM +0300, Cristian Ciocaltea wrote:
>> drm_atomic_helper_connector_hdmi_hotplug() does not currently
>> synchronize SCDC status on hotplug events, leaving the scrambler state
>> potentially inconsistent after (re)connect.
>>
>> Hook drm_connector_hdmi_sync_scdc() into both the connect and disconnect
>> paths, replacing the existing TODOs around missing scrambler handling.
>>
>> SCDC synchronization may require a CRTC reset, which in turn needs a
>> modeset acquire context for correct locking.  Therefore, extend
>> drm_atomic_helper_connector_hdmi_hotplug() and
>> drm_atomic_helper_connector_hdmi_update() to take a
>> drm_modeset_acquire_ctx argument.  Additionally, change their return
>> type from void to int, allowing propagation of errors, such as -EDEADLK
>> from lock contention.
>>
>> Update existing callers to pass NULL for the acquire context, preserving
>> current behavior.
> 
> You should have two patches here: one to change the prototype of the
> helpers, and one to add the call to drm_connector_hdmi_sync_scdc

Ack.

>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
>> ---
>>  drivers/gpu/drm/display/drm_bridge_connector.c  |  3 ++-
>>  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 28 +++++++++++++++++--------
>>  drivers/gpu/drm/vc4/vc4_hdmi.c                  |  2 +-
>>  include/drm/display/drm_hdmi_state_helper.h     |  6 ++++--
>>  4 files changed, 26 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
>> index 796069dbf1a1..46104506fe32 100644
>> --- a/drivers/gpu/drm/display/drm_bridge_connector.c
>> +++ b/drivers/gpu/drm/display/drm_bridge_connector.c
>> @@ -221,7 +221,8 @@ drm_bridge_connector_detect(struct drm_connector *connector, bool force)
>>  		status = detect->funcs->detect(detect, connector);
>>  
>>  		if (hdmi)
>> -			drm_atomic_helper_connector_hdmi_hotplug(connector, status);
>> +			drm_atomic_helper_connector_hdmi_hotplug(connector, status,
>> +								 NULL);
>>  
>>  		drm_bridge_connector_hpd_notify(connector, status);
>>  	} else {
> 
> We should move this one to detect_ctx to get the ctx passed and avoid
> passing NULL here.

We do this in patch 15.  Should I try to reorder?

>> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>> index db76699093e8..69ccfbf123fe 100644
>> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>> @@ -1198,18 +1198,20 @@ drm_atomic_helper_connector_hdmi_clear_audio_infoframe(struct drm_connector *con
>>  }
>>  EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_clear_audio_infoframe);
>>  
>> -static void
>> +static int
>>  drm_atomic_helper_connector_hdmi_update(struct drm_connector *connector,
>> -					enum drm_connector_status status)
>> +					enum drm_connector_status status,
>> +					struct drm_modeset_acquire_ctx *ctx)
> 
> detect_ctx has the context first, I think we should use that convention
> here too.

Ack.

>>  {
>>  	const struct drm_edid *drm_edid;
>> +	int ret = 0;
>>  
>>  	if (status == connector_status_disconnected) {
>> -		// TODO: also handle scramber, HDMI sink disconnected.
>> +		ret = drm_connector_hdmi_sync_scdc(connector, false, ctx);
>>  		drm_connector_hdmi_audio_plugged_notify(connector, false);
>>  		drm_edid_connector_update(connector, NULL);
>>  		drm_connector_cec_phys_addr_invalidate(connector);
>> -		return;
>> +		return ret;
>>  	}
>>  
>>  	if (connector->hdmi.funcs->read_edid)
>> @@ -1222,24 +1224,32 @@ drm_atomic_helper_connector_hdmi_update(struct drm_connector *connector,
>>  	drm_edid_free(drm_edid);
>>  
>>  	if (status == connector_status_connected) {
>> -		// TODO: also handle scramber, HDMI sink is now connected.
>> +		ret = drm_connector_hdmi_sync_scdc(connector, true, ctx);
>>  		drm_connector_hdmi_audio_plugged_notify(connector, true);
>>  		drm_connector_cec_phys_addr_set(connector);
>>  	}
>> +
>> +	return ret;
>>  }
>>  
>>  /**
>>   * drm_atomic_helper_connector_hdmi_hotplug - Handle the hotplug event for the HDMI connector
>>   * @connector: A pointer to the HDMI connector
>>   * @status: Connection status
>> + * @ctx: Lock acquisition context to be used for resetting CRTC
>>   *
>>   * This function should be called as a part of the .detect() / .detect_ctx()
>>   * callbacks for all status changes.
>> + *
>> + * Returns:
>> + * Zero on success, error code on failure.
>> + * If @ctx is set, it might also return -EDEADLK.
>>   */
>> -void drm_atomic_helper_connector_hdmi_hotplug(struct drm_connector *connector,
>> -					      enum drm_connector_status status)
>> +int drm_atomic_helper_connector_hdmi_hotplug(struct drm_connector *connector,
>> +					     enum drm_connector_status status,
>> +					     struct drm_modeset_acquire_ctx *ctx)
>>  {
>> -	drm_atomic_helper_connector_hdmi_update(connector, status);
>> +	return drm_atomic_helper_connector_hdmi_update(connector, status, ctx);
>>  }
>>  EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_hotplug);
>>  
>> @@ -1254,6 +1264,6 @@ EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_hotplug);
>>   */
>>  void drm_atomic_helper_connector_hdmi_force(struct drm_connector *connector)
>>  {
>> -	drm_atomic_helper_connector_hdmi_update(connector, connector->status);
>> +	drm_atomic_helper_connector_hdmi_update(connector, connector->status, NULL);
>>  }
> 
> We should create a new context here.

Ack.

> 
>>  EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_force);
>> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
>> index 74dce4be0c00..e165f604939b 100644
>> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
>> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
>> @@ -375,7 +375,7 @@ static void vc4_hdmi_handle_hotplug(struct vc4_hdmi *vc4_hdmi,
>>  	 * the lock for now.
>>  	 */
>>  
>> -	drm_atomic_helper_connector_hdmi_hotplug(connector, status);
>> +	drm_atomic_helper_connector_hdmi_hotplug(connector, status, NULL);
> 
> vc4_hdmi_handle_hotplug has the context passed as an argument, we should reuse it.

The vc4 conversion (patch 31) removes vc4_hdmi_handle_hotplug() and calls
drm_atomic_helper_connector_hdmi_hotplug() directly in
vc4_hdmi_connector_detect_ctx().  

I used NULL here to ensure there wouldn't be any race between the two separate
SCDC state management implementations, but that can't happen at this point
anyway (hdmi->scrambler_enabled isn't set by the driver).  So we can pass the
context if you prefer.

Thanks,
Cristian