[PATCH] drm: Print some debug/error info during DP dual mode detect

[Imre Deak]

On Wed, 2016-10-26 at 18:10 +0300, Ville Syrjälä wrote:
> On Wed, Oct 26, 2016 at 05:50:08PM +0300, Imre Deak wrote:
> > There's at least one LSPCON device that occasionally returns an unexpected
> > adaptor ID which leads to a failed detect. Print some debug info to help
> > debugging this and future cases. Also print an error for an unexpected
> > adaptor ID, so users can report it.
> > 
> > Cc: dri-devel at lists.freedesktop.org
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > ---
> >  drivers/gpu/drm/drm_dp_dual_mode_helper.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c 
> > b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> > index 488355b..a0e603b 100644
> > --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> > @@ -142,6 +142,11 @@ static bool is_hdmi_adaptor(const char 
> > hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
> >                  sizeof(dp_dual_mode_hdmi_id)) == 0;
> >  }
> >  
> > +static bool is_type1_adaptor(uint8_t adaptor_id)
> > +{
> > +   return adaptor_id == 0 || adaptor_id == 0xff;
> > +}
> > +
> >  static bool is_type2_adaptor(uint8_t adaptor_id)
> >  {
> >    return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
> > @@ -193,6 +198,8 @@ enum drm_dp_dual_mode_type 
> > drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
> >     */
> >    ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
> >                                hdmi_id, sizeof(hdmi_id));
> > +   DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
> > +                 ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
> 
> What does that %*pE print with size==0, nothing?

Yes.

> >    if (ret)
> >            return DRM_DP_DUAL_MODE_UNKNOWN;
> >  
> > @@ -210,6 +217,8 @@ enum drm_dp_dual_mode_type 
> > drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
> >     */
> >    ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
> >                                &adaptor_id, sizeof(adaptor_id));
> > +   DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
> > +                 adaptor_id, ret);
> >    if (ret == 0) {
> >            if (is_lspcon_adaptor(hdmi_id, adaptor_id))
> >                    return DRM_DP_DUAL_MODE_LSPCON;
> > @@ -219,6 +228,10 @@ enum drm_dp_dual_mode_type 
> > drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
> >                    else
> >                            return DRM_DP_DUAL_MODE_TYPE2_DVI;
> >            }
> > +           if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
>                                        
>               ^^^^^^^^^^^^^^^^^^^^^^^^
> I take it that was to account for the broken adaptors that ignore the
> offset?

Yep.

> > +                   DRM_ERROR("Unexpected DP dual mode adapter ID %02x\n",
> > +                             adaptor_id);
> 
> s/adapter/adaptor/ since that's what the spec called it, and I continued
> down the same path to not confuse it the the i2c adapter.

Ok.

> With that
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> > +
> >    }
> >  
> >    if (is_hdmi_adaptor(hdmi_id))
> > -- 
> > 2.5.0
>