[Intel-gfx] [PATCH] drm/i915: Update the status of connector when receiving MST unplug event

[Daniel Vetter]

On Wed, Aug 02, 2017 at 01:49:18AM +0000, Pandiyan, Dhinakaran wrote:
> 
> On Tue, 2017-08-01 at 16:51 +0800, Ethan Hsieh wrote:
> > We do not update the status of connector when receiving MST unplug event.
> > Call detect function to get latest status and then update status of connector.
> > 
> 
> Cc'ing Daniel and Chris.
> 
> Thanks for sending this to the list. 
> 
> The issue is connector ref count is not zero when
> destroy_mst_connector() is called, which results in the connector not
> being freed until the userspace shuts down the crtc tied to the
> connector. But the kernel needs to update the connector status for the
> user space to shut it down.

Here's what's supposed to happen:
1. kernel sends out uevent
2. userspace does a full probe using GetConnector
3. kernel calls down into ->probe, updates connector->status
4. userspace notices the connector is disconnected, shuts down the
CRTC/connector pipe
5. Last reference is dropped, connector disappears
6. Another round of uevent for the kernel removal (I think, not sure about
this one).

I suspect your userspace fails to do 2 if you need this patch.
-Daniel

> 
> 
> > Before applying the patch:
> > [313.665321] [drm:intel_get_hpd_pins [i915]] hotplug event received, stat 0x00200000, dig 0x10101012, pins 0x00000020
> > [313.665383] [drm:intel_hpd_irq_handler [i915]] digital hpd port B - long
> > [313.665436] [drm:intel_hpd_irq_handler [i915]] Received HPD interrupt on PIN 5 - cnt: 0
> > [313.665539] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port B - long
> > [313.944743] [drm:intel_dp_destroy_mst_connector [i915]]
> > [313.944848] [drm:intel_dp_destroy_mst_connector [i915]]
> > 
> > After applying the patch:
> > [43.175798] [drm:intel_dp_destroy_mst_connector [i915]] [CONNECTOR:70:DP-4] status updated from connected to disconnected
> > [43.175870] [drm:intel_dp_destroy_mst_connector [i915]]
> > [43.177675] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:70:DP-4]
> > [43.177679] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:70:DP-4] disconnected
> > 
> > Signed-off-by: Ethan Hsieh <ethan.hsieh at canonical.com>
> 
> 
> This patch needs a Fixes: tag as it does fix a fdo bug.
> 
> 
> > ---
> >  drivers/gpu/drm/i915/intel_dp_mst.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> > index e4ea968..b02a9a8 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> > @@ -492,6 +492,20 @@ static void intel_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
> >  {
> >  	struct intel_connector *intel_connector = to_intel_connector(connector);
> >  	struct drm_i915_private *dev_priv = to_i915(connector->dev);
> > +	enum drm_connector_status old_status;
> > +
> > +	mutex_lock(&connector->dev->mode_config.mutex);
> > +	old_status = connector->status;
> > +	connector->status = connector->funcs->detect(connector, false);
> 
> Isn't detect already done by this point? destroy_connector() should be
> called after we know the display is disconnected. 
> 
> > +
> > +	if (old_status != connector->status)
> > +		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
> > +			      connector->base.id,
> > +			      connector->name,
> > +			      drm_get_connector_status_name(old_status),
> > +			      drm_get_connector_status_name(connector->status));
> > +
> > +	mutex_unlock(&connector->dev->mode_config.mutex);
> >  
> >  	drm_connector_unregister(connector);
> 
> The connector is unregistered unconditionally here, so you might as well
> set
> connector->status = connector_status_disconnected;
> 
> >  

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch