[PATCH 5/7] phy: qcom-qmp-combo: Introduce drm_bridge

[Bjorn Andersson]

The QMP combo PHY sits in an of_graph connected between the DisplayPort
controller and a USB Type-C connector (or possibly a redriver).

The TCPM needs to be able to convey the HPD signal to the DisplayPort
controller, but no directly link is provided by DeviceTree so the signal
needs to "pass through" the QMP combo phy.

Handle this by introducing a drm_bridge which upon initialization finds
the next bridge (i.e. the usb-c-connector) and chain this together. This
way HPD changes in the connector will propagate to the DisplayPort
driver.

The connector bridge is resolved lazily, as the TCPM is expected to be
able to resolve the typec mux and switch at probe time, so the QMP combo
phy will probe before the TCPM.

Signed-off-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
---
 drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 36 +++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
index 5d6d6ef3944b..84bc08002537 100644
--- a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
+++ b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
@@ -22,6 +22,8 @@
 #include <linux/usb/typec.h>
 #include <linux/usb/typec_mux.h>
 
+#include <drm/drm_bridge.h>
+
 #include <dt-bindings/phy/phy-qcom-qmp.h>
 
 #include "phy-qcom-qmp.h"
@@ -1332,6 +1334,8 @@ struct qmp_combo {
 	struct clk_hw dp_link_hw;
 	struct clk_hw dp_pixel_hw;
 
+	struct drm_bridge bridge;
+
 	struct typec_switch_dev *sw;
 	enum typec_orientation orientation;
 };
@@ -3196,6 +3200,34 @@ static int qmp_combo_register_clocks(struct qmp_combo *qmp, struct device_node *
 	return devm_add_action_or_reset(qmp->dev, phy_clk_release_provider, dp_np);
 }
 
+static int qmp_combo_bridge_attach(struct drm_bridge *bridge,
+				   enum drm_bridge_attach_flags flags)
+{
+	struct qmp_combo *qmp = container_of(bridge, struct qmp_combo, bridge);
+	struct drm_bridge *next_bridge;
+
+	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
+		return -EINVAL;
+
+	next_bridge = devm_drm_of_get_bridge(qmp->dev, qmp->dev->of_node, 0, 0);
+	if (IS_ERR(next_bridge))
+		return dev_err_probe(qmp->dev, PTR_ERR(next_bridge), "failed to acquire drm_bridge\n");
+
+	return drm_bridge_attach(bridge->encoder, next_bridge, bridge, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+}
+
+static const struct drm_bridge_funcs qmp_combo_bridge_funcs = {
+	.attach	= qmp_combo_bridge_attach,
+};
+
+static int qmp_combo_dp_register_bridge(struct qmp_combo *qmp)
+{
+	qmp->bridge.funcs = &qmp_combo_bridge_funcs;
+	qmp->bridge.of_node = qmp->dev->of_node;
+
+	return devm_drm_bridge_add(qmp->dev, &qmp->bridge);
+}
+
 static int qmp_combo_parse_dt_lecacy_dp(struct qmp_combo *qmp, struct device_node *np)
 {
 	struct device *dev = qmp->dev;
@@ -3459,6 +3491,10 @@ static int qmp_combo_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ret = qmp_combo_dp_register_bridge(qmp);
+	if (ret)
+		return ret;
+
 	/* Check for legacy binding with child nodes. */
 	usb_np = of_get_child_by_name(dev->of_node, "usb3-phy");
 	if (usb_np) {
-- 
2.39.2