Re: [RFC PATCH v2 2/5] drm/msm/dp: support attaching bridges to the DP encoder

[Kuogee Hsieh]

On 2/11/2022 2:40 PM, Dmitry Baryshkov wrote:

Currently DP driver will allocate panel bridge for eDP panels. This
supports only the following topology:

- eDP encoder ⇒ eDP panel (wrapped using panel-bridge)

Simplify this code to just check if there is any next bridge in the
chain (be it a panel bridge or regular bridge). Rename panel_bridge
field to next_bridge accordingly.

This allows one to use e.g. one of the following display topologies:

- eDP encoder ⇒ ptn3460 ⇒ fixed LVDS panel
- eDP encoder ⇒ ptn3460 ⇒ LVDS connector with EDID lines for panel autodetect
- eDP encoder ⇒ ptn3460 ⇒ THC63LVD1024 ⇒ DPI panel.
- eDP encoder ⇒ LT8912 ⇒ DSI panel

Signed-off-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org>

Tested-by: Kuogee Hsieh <quic_khs...@quicinc.com>

---
  drivers/gpu/drm/msm/dp/dp_display.c |  2 +-
  drivers/gpu/drm/msm/dp/dp_display.h |  2 +-
  drivers/gpu/drm/msm/dp/dp_drm.c     |  4 ++--
  drivers/gpu/drm/msm/dp/dp_parser.c  | 31 +++++++++++++++--------------
  drivers/gpu/drm/msm/dp/dp_parser.h  |  2 +-
  5 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
b/drivers/gpu/drm/msm/dp/dp_display.c
index 44d42c76c2a3..45f9a912ecc5 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -266,7 +266,7 @@ static int dp_display_bind(struct device *dev, struct 
device *master,
                goto end;
        }

- dp->dp_display.panel_bridge = dp->parser->panel_bridge;

+       dp->dp_display.next_bridge = dp->parser->next_bridge;

dp->aux->drm_dev = drm;

        rc = dp_aux_register(dp->aux);
diff --git a/drivers/gpu/drm/msm/dp/dp_display.h 
b/drivers/gpu/drm/msm/dp/dp_display.h
index e3adcd578a90..7af2b186d2d9 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.h
+++ b/drivers/gpu/drm/msm/dp/dp_display.h
@@ -16,7 +16,7 @@ struct msm_dp {
        struct drm_bridge *bridge;
        struct drm_connector *connector;
        struct drm_encoder *encoder;
-       struct drm_bridge *panel_bridge;
+       struct drm_bridge *next_bridge;
        bool is_connected;
        bool audio_enabled;
        bool power_on;
diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
index 26ef41a4c1b6..80f59cf99089 100644
--- a/drivers/gpu/drm/msm/dp/dp_drm.c
+++ b/drivers/gpu/drm/msm/dp/dp_drm.c
@@ -236,9 +236,9 @@ struct drm_bridge *msm_dp_bridge_init(struct msm_dp 
*dp_display, struct drm_devi
                return ERR_PTR(rc);
        }

- if (dp_display->panel_bridge) {

+       if (dp_display->next_bridge) {
                rc = drm_bridge_attach(dp_display->encoder,
-                                       dp_display->panel_bridge, bridge,
+                                       dp_display->next_bridge, bridge,
                                        DRM_BRIDGE_ATTACH_NO_CONNECTOR);
                if (rc < 0) {
                        DRM_ERROR("failed to attach panel bridge: %d\n", rc);
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c 
b/drivers/gpu/drm/msm/dp/dp_parser.c
index a7acc23f742b..901d7967370f 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -265,23 +265,16 @@ static int dp_parser_clock(struct dp_parser *parser)
        return 0;
  }

-static int dp_parser_find_panel(struct dp_parser *parser)

+static int dp_parser_find_next_bridge(struct dp_parser *parser)
  {
        struct device *dev = &parser->pdev->dev;
-       struct drm_panel *panel;
-       int rc;
+       struct drm_bridge *bridge;

- rc = drm_of_find_panel_or_bridge(dev->of_node, 1, 0, &panel, NULL);

-       if (rc) {
-               DRM_ERROR("failed to acquire DRM panel: %d\n", rc);
-               return rc;
-       }
+       bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
+       if (IS_ERR(bridge))
+               return PTR_ERR(bridge);

- parser->panel_bridge = devm_drm_panel_bridge_add(dev, panel);

-       if (IS_ERR(parser->panel_bridge)) {
-               DRM_ERROR("failed to create panel bridge\n");
-               return PTR_ERR(parser->panel_bridge);
-       }
+       parser->next_bridge = bridge;

return 0;

  }
@@ -307,10 +300,18 @@ static int dp_parser_parse(struct dp_parser *parser, int 
connector_type)
        if (rc)
                return rc;

+ /*

+        * Currently we support external bridges only for eDP connectors.
+        *
+        * No external bridges are expected for the DisplayPort connector,
+        * it is physically present in a form of a DP or USB-C connector.
+        */
        if (connector_type == DRM_MODE_CONNECTOR_eDP) {
-               rc = dp_parser_find_panel(parser);
-               if (rc)
+               rc = dp_parser_find_next_bridge(parser);
+               if (rc) {
+                       DRM_ERROR("DP: failed to find next bridge\n");
                        return rc;
+               }
        }

/* Map the corresponding regulator information according to

diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h 
b/drivers/gpu/drm/msm/dp/dp_parser.h
index 3172da089421..4cec851e38d9 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.h
+++ b/drivers/gpu/drm/msm/dp/dp_parser.h
@@ -123,7 +123,7 @@ struct dp_parser {
        struct dp_display_data disp_data;
        const struct dp_regulator_cfg *regulator_cfg;
        u32 max_dp_lanes;
-       struct drm_bridge *panel_bridge;
+       struct drm_bridge *next_bridge;

int (*parse)(struct dp_parser *parser, int connector_type);

  };