[PATCH v5 1/2] drm: Add detection of changing of edid on between suspend and resume

[Lisovskiy, Stanislav]

On Thu, 2019-04-11 at 17:36 +0300, Gwan-gyeong Mun wrote:
> The hotplug detection routine of drm_helper_hpd_irq_event() can
> detect
> changing of status of connector, but it can not detect changing of
> edid.
> 
> Following scenario requires detection of changing of edid.
> 
>  1) plug display device to a connector
>  2) system suspend
>  3) unplug 1)'s display device and plug the other display device to a
>     connector
>  4) system resume
> 
> It adds edid check routine when a connector status still remains as
> "connector_status_connected".
> 
> v2: Add NULL check before comparing of EDIDs.
> v3: Make it as part of existing drm_helper_hpd_irq_event() (Stan,
> Mika)
> v4: Rebased
> v5: Use a cached edid property blob data of connector instead of
> adding
>     a new detected_edid variable. (Maarten)
>     Add an using of reference count for getting a cached edid
> property
>     blob data. (Maarten)
> 
> Testcase: igt/kms_chamelium/hdmi-edid-change-during-hibernate
> Testcase: igt/kms_chamelium/hdmi-edid-change-during-suspend
> Testcase: igt/kms_chamelium/dp-edid-change-during-hibernate
> Testcase: igt/kms_chamelium/dp-edid-change-during-suspend
> 
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> ---
>  drivers/gpu/drm/drm_probe_helper.c | 34
> +++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_probe_helper.c
> b/drivers/gpu/drm/drm_probe_helper.c
> index 6fd08e04b323..27ad7f3dabb7 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -742,7 +742,16 @@ EXPORT_SYMBOL(drm_kms_helper_poll_fini);
>   * panels.
>   *
>   * This helper function is useful for drivers which can't or don't
> track hotplug
> - * interrupts for each connector.
> + * interrupts for each connector. And it also supports a detection
> of changing
> + * of edid on between suspend and resume when a connector status
> still remains
> + * as "connector_status_connected".
> + *
> + * Following scenario requires detection of changing of edid.
> + *  1) plug display device to a connector
> + *  2) system suspend
> + *  3) unplug 1)'s display device and plug the other display device
> to a
> + *     connector
> + *  4) system resume
>   *
>   * Drivers which support hotplug interrupts for each connector
> individually and
>   * which have a more fine-grained detect logic should bypass this
> code and
> @@ -760,6 +769,7 @@ bool drm_helper_hpd_irq_event(struct drm_device
> *dev)
>  	struct drm_connector *connector;
>  	struct drm_connector_list_iter conn_iter;
>  	enum drm_connector_status old_status;
> +	struct drm_property_blob *old_edid_blob_ptr;
>  	bool changed = false;
>  
>  	if (!dev->mode_config.poll_enabled)
> @@ -774,6 +784,11 @@ bool drm_helper_hpd_irq_event(struct drm_device
> *dev)
>  
>  		old_status = connector->status;
>  
> +		if (connector->edid_blob_ptr)
> +			old_edid_blob_ptr =
> drm_property_blob_get(connector->edid_blob_ptr);
> +		else
> +			old_edid_blob_ptr = NULL;
> +
>  		connector->status = drm_helper_probe_detect(connector,
> NULL, false);
>  		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s
> to %s\n",
>  			      connector->base.id,
> @@ -782,6 +797,23 @@ bool drm_helper_hpd_irq_event(struct drm_device
> *dev)
>  			      drm_get_connector_status_name(connector-
> >status));
>  		if (old_status != connector->status)
>  			changed = true;
> +
> +		/* Check changing of edid when a connector status still
> remains
> +		 * as "connector_status_connected".
> +		 */
> +		if (old_edid_blob_ptr && connector->edid_blob_ptr &&

I guess you don't need to check both old_edid_blob_ptr && connector-
>edid_blob_ptr here. Because if old_edid_blob_ptr is not NULL - it
means that connector->edid_blob_ptr was not NULL for sure. See the 
condition you have added above.
I mean this one:

> +		if (connector->edid_blob_ptr)
> +			old_edid_blob_ptr =
> drm_property_blob_get(connector->edid_blob_ptr);
> +		else
> +			old_edid_blob_ptr = NULL;

So I would check only old_edid_blob_ptr for not being NULL here.



> +		    old_status == connector->status &&
> +		    old_status == connector_status_connected) {
> +			if (memcmp(old_edid_blob_ptr->data,
> +				connector->edid_blob_ptr->data,
> +				old_edid_blob_ptr->length)) {
> +				changed = true;
> +				DRM_DEBUG_KMS("[CONNECTOR:%d:%s] edid
> updated\n",
> +					      connector->base.id,
> +					      connector->name);
> +			}
> +		}
> +		drm_property_blob_put(old_edid_blob_ptr);
>  	}
>  	drm_connector_list_iter_end(&conn_iter);
>  	mutex_unlock(&dev->mode_config.mutex);