[Intel-gfx] [PATCH v2] drm/i915/dp: Update connector status for DP MST hotplugs

[Pandiyan, Dhinakaran]

On Tue, 2016-11-08 at 13:04 +0200, Ville Syrjälä wrote:
> On Mon, Nov 07, 2016 at 04:27:30PM -0800, Dhinakaran Pandiyan wrote:
> > Hotplugging a monitor in DP MST configuration triggers short pulses.
> > Although the short pulse handling path ends up in the MST hotplug function,
> > we do not perform a detect before sending the hotplug uvent. This leads to
> > the connector status not being updated when the userspace calls
> > DRM_IOCTL_MODE_GETCONNECTOR.
> > 
> > So, let's call the connector function ->detect() to update the connector
> > status before sending the uevent.
> > 
> > v2: Update connector status inside mode_config mutex (Ville)
> > 
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp_mst.c | 22 +++++++++++++++++++++-
> >  1 file changed, 21 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> > index 3ffbd69..8e36a96 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> > @@ -492,8 +492,28 @@ static void intel_dp_mst_hotplug(struct drm_dp_mst_topology_mgr *mgr)
> >  	struct intel_dp *intel_dp = container_of(mgr, struct intel_dp, mst_mgr);
> >  	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> >  	struct drm_device *dev = intel_dig_port->base.base.dev;
> > +	struct intel_connector *intel_connector;
> > +	bool changed = false;
> > +	enum drm_connector_status old_status;
> > +	struct drm_mode_config *mode_config = &dev->mode_config;
> > +
> > +	mutex_lock(&mode_config->mutex);
> > +	for_each_intel_connector(dev, intel_connector) {
> > +		struct drm_connector *connector = &(intel_connector->base);
> > +
> > +		if (intel_connector->mst_port != intel_dp)
> > +			continue;
> > +
> > +		old_status = connector->status;
> > +		connector->status = connector->funcs->detect(connector, false);
> > +
> > +		if (old_status != connector->status)
> > +			changed = true;
> > +	}
> > +	mutex_unlock(&mode_config->mutex);
> 
> To help reviewers it might be nice to have a short explanation of the
> locking situation in the commit message, mainly why is it safe to simply
> take mode_config.mutex here.
> 

I can't convince myself this locking is correct yet.
drm_dp_send_link_address(), one of the callers of this function is
recursive.
drm_dp_send_link_address()->drm_dp_add_port()->drm_dp_send_link_address()

I am wondering if hpd_pulse should return IRQ_NONE so that we can have
->detect() called from the hotplug work function. For this to work,
we'll need to change drm_dp_mst_hpd_irq().


-DK

> >  
> > -	drm_kms_helper_hotplug_event(dev);
> > +	if (changed)
> > +		drm_kms_helper_hotplug_event(dev);
> >  }
> >  
> >  static const struct drm_dp_mst_topology_cbs mst_cbs = {
> > -- 
> > 2.7.4
>