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

[Mun, Gwan-gyeong]

On Thu, 2019-04-11 at 17:00 +0100, Lisovskiy, Stanislav wrote:
> 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.
> 
> 
Hi Stan,

Thank you for checking it.

First, drivers could set edid_blob_ptr to NULL with
drm_connector_update_edid_property().
And drm_helper_probe_detect() could lead updating of an internal edid
of driver and if driver can not get EDID from I2C, it could call
drm_connector_update_edid_property() with NULL.

therefore I think that we should check old and new edid_blob_ptr are
NULL or not.
> 
> > +		    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);