Re: [RFC PATCH v2 1/5] drm/msm/dp: fix panel bridge attachment

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 19/02/2022 02:56, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2022-02-11 14:40:02)
>> In commit 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display
>> enable and disable") the DP driver received a drm_bridge instance, which
>> is always attached to the encoder as a root bridge. However it conflicts
>> with the panel_bridge support for eDP panels. The panel bridge attaches
>> to the encoder before the "dp" bridge has a chace to do so. Change
> 
> s/chace/chance/
> 
>> panel_bridge attachment to come after dp_bridge attachment.
> 
> s/panel_bridge/panel bridge/ possibly? And maybe clarify that dp_bridge
> is the "DP driver's drm_bridge instance created in
> msm_dp_bridge_init()"?
> 
> My understanding is that we want to pass the bridge created in
> msm_dp_bridge_init() as the 'previous' bridge so that it attaches the
> panel bridge to the output of the DP bridge that's attached to the
> encoder.

Thanks! I'll update the commit log when pushing the patches.

> 
>>
>> Fixes: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable and disable")
>> Cc: Kuogee Hsieh <quic_khsieh@quicinc.com>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>> ---
> 
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>
> 
>>   drivers/gpu/drm/msm/dp/dp_drm.c | 21 +++++++++++----------
>>   1 file changed, 11 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
>> index d4d360d19eba..26ef41a4c1b6 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>> @@ -169,16 +169,6 @@ struct drm_connector *dp_drm_connector_init(struct msm_dp *dp_display)
>>
>>          drm_connector_attach_encoder(connector, dp_display->encoder);
>>
>> -       if (dp_display->panel_bridge) {
>> -               ret = drm_bridge_attach(dp_display->encoder,
>> -                                       dp_display->panel_bridge, NULL,
>> -                                       DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>> -               if (ret < 0) {
>> -                       DRM_ERROR("failed to attach panel bridge: %d\n", ret);
>> -                       return ERR_PTR(ret);
>> -               }
>> -       }
>> -
>>          return connector;
>>   }
>>
>> @@ -246,5 +236,16 @@ struct drm_bridge *msm_dp_bridge_init(struct msm_dp *dp_display, struct drm_devi
>>                  return ERR_PTR(rc);
>>          }
>>
>> +       if (dp_display->panel_bridge) {
>> +               rc = drm_bridge_attach(dp_display->encoder,
>> +                                       dp_display->panel_bridge, bridge,
>> +                                       DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>> +               if (rc < 0) {
>> +                       DRM_ERROR("failed to attach panel bridge: %d\n", rc);
>> +                       drm_bridge_remove(bridge);
>> +                       return ERR_PTR(rc);
>> +               }
>> +       }
>> +
>>          return bridge;
> 
> Not a problem with this patch, but what is this pointer used for? I see
> it's assigned to priv->bridges and num_bridges is incremented but nobody
> seems to look at that.


That's on my todo list. to remove connectors array and to destroy 
created bridges during drm device destruction.

-- 
With best wishes
Dmitry