From da9bf68c5fa50fb5feda3a6f8b994a5378f97559 Mon Sep 17 00:00:00 2001
From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Date: Thu, 14 May 2020 04:03:07 +0300
Subject: drm: bridge: dw-hdmi: Attach to next bridge if available
Git-commit: 5bcc48395b9f35dace564de47fcf434cdb67a8e1
Patch-mainline: v5.15-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

On all platforms except i.MX and Rockchip, the dw-hdmi DT bindings
require a video output port connected to an HDMI sink (most likely an
HDMI connector, in rare cases another bridges converting HDMI to another
protocol). For those platforms, retrieve the next bridge and attach it
from the dw-hdmi bridge attach handler.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com> # On V3U
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 54 ++++++++++++++++++++++-
 include/drm/bridge/dw_hdmi.h              |  2 +
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 77af49248069..f08d0fded61f 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -143,6 +143,7 @@ struct dw_hdmi_phy_data {
 struct dw_hdmi {
 	struct drm_connector connector;
 	struct drm_bridge bridge;
+	struct drm_bridge *next_bridge;
 
 	unsigned int version;
 
@@ -2775,7 +2776,8 @@ static int dw_hdmi_bridge_attach(struct drm_bridge *bridge,
 	struct dw_hdmi *hdmi = bridge->driver_private;
 
 	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
-		return 0;
+		return drm_bridge_attach(bridge->encoder, hdmi->next_bridge,
+					 bridge, flags);
 
 	return dw_hdmi_connector_create(hdmi);
 }
@@ -3160,6 +3162,52 @@ static void dw_hdmi_init_hw(struct dw_hdmi *hdmi)
 /* -----------------------------------------------------------------------------
  * Probe/remove API, used from platforms based on the DRM bridge API.
  */
+
+static int dw_hdmi_parse_dt(struct dw_hdmi *hdmi)
+{
+	struct device_node *endpoint;
+	struct device_node *remote;
+
+	if (!hdmi->plat_data->output_port)
+		return 0;
+
+	endpoint = of_graph_get_endpoint_by_regs(hdmi->dev->of_node,
+						 hdmi->plat_data->output_port,
+						 -1);
+	if (!endpoint) {
+		/*
+		 * On platforms whose bindings don't make the output port
+		 * mandatory (such as Rockchip) the plat_data->output_port
+		 * field isn't set, so it's safe to make this a fatal error.
+		 */
+		dev_err(hdmi->dev, "Missing endpoint in port@%u\n",
+			hdmi->plat_data->output_port);
+		return -ENODEV;
+	}
+
+	remote = of_graph_get_remote_port_parent(endpoint);
+	of_node_put(endpoint);
+	if (!remote) {
+		dev_err(hdmi->dev, "Endpoint in port@%u unconnected\n",
+			hdmi->plat_data->output_port);
+		return -ENODEV;
+	}
+
+	if (!of_device_is_available(remote)) {
+		dev_err(hdmi->dev, "port@%u remote device is disabled\n",
+			hdmi->plat_data->output_port);
+		of_node_put(remote);
+		return -ENODEV;
+	}
+
+	hdmi->next_bridge = of_drm_find_bridge(remote);
+	of_node_put(remote);
+	if (!hdmi->next_bridge)
+		return -EPROBE_DEFER;
+
+	return 0;
+}
+
 struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
 			      const struct dw_hdmi_plat_data *plat_data)
 {
@@ -3196,6 +3244,10 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
 	mutex_init(&hdmi->cec_notifier_mutex);
 	spin_lock_init(&hdmi->audio_lock);
 
+	ret = dw_hdmi_parse_dt(hdmi);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
 	ddc_node = of_parse_phandle(np, "ddc-i2c-bus", 0);
 	if (ddc_node) {
 		hdmi->ddc = of_get_i2c_adapter_by_node(ddc_node);
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index 6a5716655619..2a1f85f9a8a3 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -126,6 +126,8 @@ struct dw_hdmi_phy_ops {
 struct dw_hdmi_plat_data {
 	struct regmap *regm;
 
+	unsigned int output_port;
+
 	unsigned long input_bus_encoding;
 	bool use_drm_infoframe;
 	bool ycbcr_420_allowed;
-- 
2.38.1