[PATCH 4/4] drm/dp/mst: Check peer device type before attempting EDID read

[Ville Syrjälä]

On Wed, Oct 26, 2016 at 02:55:14PM +0200, Daniel Vetter wrote:
> On Wed, Oct 26, 2016 at 12:05:55PM +0300, ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Only certain types of pdts have the DDC bus registered, so check for
> > that before we attempt the EDID read. Othwewise we risk playing around
> > with an i2c adapter that doesn't actually exist.
> > 
> > Cc: stable at vger.kernel.org
> > Cc: Carlos Santa <carlos.santa at intel.com>
> > Cc: Kirill A. Shutemov <kirill at shutemov.name>
> > Tested-by: Carlos Santa <carlos.santa at intel.com>
> > Tested-by: Kirill A. Shutemov <kirill at shutemov.name>
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97666
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_dp_mst_topology.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index 956babc161e5..690d1b407a90 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -1162,7 +1162,9 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
> >  			drm_dp_put_port(port);
> >  			goto out;
> >  		}
> > -		if (port->port_num >= DP_MST_LOGICAL_PORT_0) {
> > +		if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
> > +		     port->pdt == DP_PEER_DEVICE_SST_SINK) &&
> > +		    port->port_num >= DP_MST_LOGICAL_PORT_0) {
> 
> Matches what's in drm_dp_port_setup_pdt. Not sure this is the most
> reliable way to do this though, but I can't come up with anything better.

Yeah. I just went with whatever looks semi-correct based on where the
thing is set up. I'd have to go read the actual spec to figure out if
this makes any real sense. But at least it avoids the explosion.

> 
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> >  			port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
> >  			drm_mode_connector_set_tile_property(port->connector);
> >  		}
> > -- 
> > 2.7.4
> > 
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> > dri-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel OTC