Re: [PATCH v10 1/4] drm/msm/dp: Add eDP support via aux_bus

From: Dmitry Baryshkov
Date: Fri May 06 2022 - 17:05:57 EST

On 07/05/2022 00:03, Abhinav Kumar wrote:


On 5/6/2022 1:49 PM, Dmitry Baryshkov wrote:
On 25/04/2022 14:44, Sankeerth Billakanti wrote:
This patch adds support for generic eDP sink through aux_bus. The eDP/DP
controller driver should support aux transactions originating from the
panel-edp driver and hence should be initialized and ready.

The panel bridge supporting the panel should be ready before the bridge
connector is initialized. The generic panel probe needs the controller
resources to be enabled to support the aux transactions originating from
the panel probe.

Signed-off-by: Sankeerth Billakanti <quic_sbillaka@xxxxxxxxxxx>
Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>

An additional side effect from this patch. Previously missing panel would have caused the bind error. Now it is the dp_modeset_init error, which translates to kms_hw_init returning -517. I kind ask to move the next_bridge acquisition back to the dp_bind in one of the followup patches.


This is true. But the end result would be same isnt it?

When dp_display_bind() failed earlier, it would cause master bind failure too due to component model.

Even now, it causes the same result?

Yes, it helped us to uncover several error. But I'd still prefer to have EPROBE_DEFER being returned earlier rather than later.


---
Changes in v10:
   - modify the error handling condition
   - modify the kernel doc

Changes in v9:
   - add comments for panel probe
   - modify the error handling checks

Changes in v8:
   - handle corner cases
   - add comment for the bridge ops

Changes in v7:
   - aux_bus is mandatory for eDP
   - connector type check modified to just check for eDP

Changes in v6:
   - Remove initialization
   - Fix aux_bus node leak
   - Split the patches

  drivers/gpu/drm/msm/dp/dp_display.c | 72 ++++++++++++++++++++++++++++++++++---
  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
  drivers/gpu/drm/msm/dp/dp_drm.c     | 21 ++++++++---
  drivers/gpu/drm/msm/dp/dp_parser.c  | 23 ++----------
  drivers/gpu/drm/msm/dp/dp_parser.h  | 14 +++++++-
  5 files changed, 101 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index d7a19d6..f772d84 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -10,6 +10,7 @@
  #include <linux/component.h>
  #include <linux/of_irq.h>
  #include <linux/delay.h>
+#include <drm/dp/drm_dp_aux_bus.h>
  #include "msm_drv.h"
  #include "msm_kms.h"
@@ -259,14 +260,12 @@ static int dp_display_bind(struct device *dev, struct device *master,
      dp->dp_display.drm_dev = drm;
      priv->dp[dp->id] = &dp->dp_display;
-    rc = dp->parser->parse(dp->parser, dp->dp_display.connector_type);
+    rc = dp->parser->parse(dp->parser);
      if (rc) {
          DRM_ERROR("device tree parsing failed\n");
          goto end;
      }
-    dp->dp_display.next_bridge = dp->parser->next_bridge;
-
      dp->aux->drm_dev = drm;
      rc = dp_aux_register(dp->aux);
      if (rc) {
@@ -1319,6 +1318,8 @@ static int dp_display_probe(struct platform_device *pdev)
      dp->pdev = pdev;
      dp->name = "drm_dp";
      dp->dp_display.connector_type = desc->connector_type;
+    dp->dp_display.is_edp =
+        (dp->dp_display.connector_type == DRM_MODE_CONNECTOR_eDP);
      rc = dp_init_sub_modules(dp);
      if (rc) {
@@ -1508,7 +1509,8 @@ void msm_dp_irq_postinstall(struct msm_dp *dp_display)
      dp_hpd_event_setup(dp);
-    dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
+    if (!dp_display->is_edp)
+        dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
  }
  void msm_dp_debugfs_init(struct msm_dp *dp_display, struct drm_minor *minor)
@@ -1530,6 +1532,64 @@ void msm_dp_debugfs_init(struct msm_dp *dp_display, struct drm_minor *minor)
      }
  }
+static int dp_display_get_next_bridge(struct msm_dp *dp)
+{
+    int rc;
+    struct dp_display_private *dp_priv;
+    struct device_node *aux_bus;
+    struct device *dev;
+
+    dp_priv = container_of(dp, struct dp_display_private, dp_display);
+    dev = &dp_priv->pdev->dev;
+    aux_bus = of_get_child_by_name(dev->of_node, "aux-bus");
+
+    if (aux_bus && dp->is_edp) {
+        dp_display_host_init(dp_priv);
+        dp_catalog_ctrl_hpd_config(dp_priv->catalog);
+        dp_display_host_phy_init(dp_priv);
+        enable_irq(dp_priv->irq);
+
+        /*
+         * The code below assumes that the panel will finish probing
+         * by the time devm_of_dp_aux_populate_ep_devices() returns.
+         * This isn't a great assumption since it will fail if the
+         * panel driver is probed asynchronously but is the best we
+         * can do without a bigger driver reorganization.
+         */
+        rc = devm_of_dp_aux_populate_ep_devices(dp_priv->aux);
+        of_node_put(aux_bus);
+        if (rc)
+            goto error;
+    } else if (dp->is_edp) {
+        DRM_ERROR("eDP aux_bus not found\n");
+        return -ENODEV;
+    }
+
+    /*
+     * External bridges are mandatory for eDP interfaces: one has to
+     * provide at least an eDP panel (which gets wrapped into panel-bridge).
+     *
+     * For DisplayPort interfaces external bridges are optional, so
+     * silently ignore an error if one is not present (-ENODEV).
+     */
+    rc = dp_parser_find_next_bridge(dp_priv->parser);
+    if (!dp->is_edp && rc == -ENODEV)
+        return 0;
+
+    if (!rc) {
+        dp->next_bridge = dp_priv->parser->next_bridge;
+        return 0;
+    }
+
+error:
+    if (dp->is_edp) {
+        disable_irq(dp_priv->irq);
+        dp_display_host_phy_exit(dp_priv);
+        dp_display_host_deinit(dp_priv);
+    }
+    return rc;
+}
+
  int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
              struct drm_encoder *encoder)
  {
@@ -1553,6 +1613,10 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
      dp_display->encoder = encoder;
+    ret = dp_display_get_next_bridge(dp_display);
+    if (ret)
+        return ret;
+
      dp_display->bridge = dp_bridge_init(dp_display, dev, encoder);
      if (IS_ERR(dp_display->bridge)) {
          ret = PTR_ERR(dp_display->bridge);
diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
index 49a1d89..1377cc3 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.h
+++ b/drivers/gpu/drm/msm/dp/dp_display.h
@@ -21,6 +21,7 @@ struct msm_dp {
      bool audio_enabled;
      bool power_on;
      unsigned int connector_type;
+    bool is_edp;
      hdmi_codec_plugged_cb plugged_cb;
diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
index 7ce1aca..8a75c55 100644
--- a/drivers/gpu/drm/msm/dp/dp_drm.c
+++ b/drivers/gpu/drm/msm/dp/dp_drm.c
@@ -114,10 +114,23 @@ struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct drm_device *
      bridge->funcs = &dp_bridge_ops;
      bridge->type = dp_display->connector_type;
-    bridge->ops =
-        DRM_BRIDGE_OP_DETECT |
-        DRM_BRIDGE_OP_HPD |
-        DRM_BRIDGE_OP_MODES;
+    /*
+     * Many ops only make sense for DP. Why?
+     * - Detect/HPD are used by DRM to know if a display is _physically_
+     *   there, not whether the display is powered on / finished initting.
+     *   On eDP we assume the display is always there because you can't
+     *   know until power is applied. If we don't implement the ops DRM will
+     *   assume our display is always there.
+     * - Currently eDP mode reading is driven by the panel driver. This
+     *   allows the panel driver to properly power itself on to read the
+     *   modes.
+     */
+    if (!dp_display->is_edp) {
+        bridge->ops =
+            DRM_BRIDGE_OP_DETECT |
+            DRM_BRIDGE_OP_HPD |
+            DRM_BRIDGE_OP_MODES;
+    }
      rc = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
      if (rc) {
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
index 1056b8d..4bdbf91 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -265,7 +265,7 @@ static int dp_parser_clock(struct dp_parser *parser)
      return 0;
  }
-static int dp_parser_find_next_bridge(struct dp_parser *parser)
+int dp_parser_find_next_bridge(struct dp_parser *parser)
  {
      struct device *dev = &parser->pdev->dev;
      struct drm_bridge *bridge;
@@ -279,7 +279,7 @@ static int dp_parser_find_next_bridge(struct dp_parser *parser)
      return 0;
  }
-static int dp_parser_parse(struct dp_parser *parser, int connector_type)
+static int dp_parser_parse(struct dp_parser *parser)
  {
      int rc = 0;
@@ -300,25 +300,6 @@ static int dp_parser_parse(struct dp_parser *parser, int connector_type)
      if (rc)
          return rc;
-    /*
-     * External bridges are mandatory for eDP interfaces: one has to
-     * provide at least an eDP panel (which gets wrapped into panel-bridge).
-     *
-     * For DisplayPort interfaces external bridges are optional, so
-     * silently ignore an error if one is not present (-ENODEV).
-     */
-    rc = dp_parser_find_next_bridge(parser);
-    if (rc == -ENODEV) {
-        if (connector_type == DRM_MODE_CONNECTOR_eDP) {
-            DRM_ERROR("eDP: next bridge is not present\n");
-            return rc;
-        }
-    } else if (rc) {
-        if (rc != -EPROBE_DEFER)
-            DRM_ERROR("DP: error parsing next bridge: %d\n", rc);
-        return rc;
-    }
-
      /* Map the corresponding regulator information according to
       * version. Currently, since we only have one supported platform,
       * mapping the regulator directly.
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
index d371bae..3a4d797 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.h
+++ b/drivers/gpu/drm/msm/dp/dp_parser.h
@@ -125,7 +125,7 @@ struct dp_parser {
      u32 max_dp_lanes;
      struct drm_bridge *next_bridge;
-    int (*parse)(struct dp_parser *parser, int connector_type);
+    int (*parse)(struct dp_parser *parser);
  };
  /**
@@ -141,4 +141,16 @@ struct dp_parser {
   */
  struct dp_parser *dp_parser_get(struct platform_device *pdev);
+/**
+ * dp_parser_find_next_bridge() - find an additional bridge to DP
+ *
+ * @parser: dp_parser data from client
+ *
+ * This function is used to find any additional bridge attached to
+ * the DP controller. The eDP interface requires a panel bridge.
+ *
+ * Return: 0 if able to get the bridge, otherwise negative errno for failure.
+ */
+int dp_parser_find_next_bridge(struct dp_parser *parser);
+
  #endif




--
With best wishes
Dmitry