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

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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@xxxxxxxxxxx>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---

Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>

  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



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