[PATCH] drm/i915/hdmi: Fix weak connector detection

[Ville Syrjälä]

On Fri, Apr 01, 2016 at 12:38:11PM -0300, Ezequiel Garcia wrote:
> El abr. 1, 2016 11:47 AM, "Ville Syrjälä" <ville.syrjala at linux.intel.com>
> escribió:
> >
> > On Thu, Mar 31, 2016 at 05:55:03PM -0300, Ezequiel Garcia wrote:
> > > Currently, our implementation of drm_connector_funcs.detect is
> > > based on getting a valid EDID.
> > >
> > > This requirement makes the driver fail to detect connected
> > > connectors in case of EDID corruption, which prevents from falling
> > > back to modes provided by builtin or user-provided EDIDs.
> >
> > So why are you getting corrupted EDIDs?
> >
> 
> Does it matter?

Yes. We should fix the real cause (if possible) instead of adding
more duct tape.

> 
> > >
> > > Let's fix this by improving the detection, with a DDC probe,
> > > if the current EDID-based detection failed.
> > >
> > > Note that a better way of dealing with this could calling
> > > drm_probe_ddc in drm_connector_funcs.detect, and do the
> > > EDID full reading and parsing in drm_connector_helper_funcs.get_modes,
> > > when it's actually needed.
> > >
> > > However, this would be more invasive and thus more error-prone.
> > > The current commit is an attempt to get some uninvasive fix,
> > > and allow for easier backporting.
> > >
> > > Signed-off-by: Ezequiel Garcia <ezequiel at vanguardiasur.com.ar>
> > > ---
> > >  drivers/gpu/drm/i915/intel_hdmi.c | 14 ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> b/drivers/gpu/drm/i915/intel_hdmi.c
> > > index a0d8daed2470..c079206e6681 100644
> > > --- a/drivers/gpu/drm/i915/intel_hdmi.c
> > > +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> > > @@ -1428,6 +1428,20 @@ intel_hdmi_detect(struct drm_connector
> *connector, bool force)
> > >       } else
> > >               status = connector_status_disconnected;
> > >
> > > +     /*
> > > +      * The above call to intel_hdmi_set_edid() checked for a valid
> EDID.
> > > +      * However, the EDID can get corrupted for several reasons,
> resulting
> > > +      * in a disconnected status despite the connector being connected.
> > > +      * Hence, let's try one more time, by only probing the DDC.
> > > +      *
> > > +      * This allows the DRM core to fallback to builtin or
> user-provided
> > > +      * EDID firmware, e.g. in drm_helper_probe_single_connector_modes.
> > > +      */
> > > +     if (status == connector_status_disconnected)
> > > +             if (drm_probe_ddc(intel_gmbus_get_adapter(dev_priv,
> > > +                                             intel_hdmi->ddc_bus)))
> > > +                     status = connector_status_connected;
> > > +
> > >       intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);
> > >
> > >       return status;
> > > --
> > > 2.7.0
> > >
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> > --
> > Ville Syrjälä
> > Intel OTC

-- 
Ville Syrjälä
Intel OTC