[PATCH v15 16/16] phy: rockchip: usbdp: Register DP aux bridge

[Sebastian Reichel <sebastian.reichel@collabora.com>]

Add support to use USB-C connectors with the DP altmode helper code on
devicetree based platforms. To get this working there must be a DRM
bridge chain from the DisplayPort controller to the USB-C connector.
E.g. on Rockchip RK3576:

root@rk3576 # cat /sys/kernel/debug/dri/0/encoder-0/bridges
bridge[0]: dw_dp_bridge_funcs
        refcount: 7
        type: [10] DP
        OF: /soc/dp@27e40000:rockchip,rk3576-dp
        ops: [0x47] detect edid hpd
bridge[1]: drm_aux_bridge_funcs
        refcount: 4
        type: [0] Unknown
        OF: /soc/phy@2b010000:rockchip,rk3576-usbdp-phy
        ops: [0x0]
bridge[2]: drm_aux_hpd_bridge_funcs
        refcount: 5
        type: [10] DP
        OF: /soc/i2c@2ac50000/typec-portc@22/connector:usb-c-connector
        ops: [0x4] hpd

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Tested-by: Igor Paunovic <royalnet026@gmail.com> # Orange Pi 5 Plus
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
 drivers/phy/rockchip/Kconfig              |  2 ++
 drivers/phy/rockchip/phy-rockchip-usbdp.c | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/phy/rockchip/Kconfig b/drivers/phy/rockchip/Kconfig
index 14698571b607..39759bb2fa1d 100644
--- a/drivers/phy/rockchip/Kconfig
+++ b/drivers/phy/rockchip/Kconfig
@@ -136,8 +136,10 @@ config PHY_ROCKCHIP_USBDP
 	tristate "Rockchip USBDP COMBO PHY Driver"
 	depends on ARCH_ROCKCHIP && OF
 	depends on TYPEC
+	depends on DRM || DRM=n
 	select GENERIC_PHY
 	select USB_COMMON
+	select DRM_AUX_BRIDGE if DRM_BRIDGE
 	help
 	  Enable this to support the Rockchip USB3.0/DP combo PHY with
 	  Samsung IP block. This is required for USB3 support on RK3588.
diff --git a/drivers/phy/rockchip/phy-rockchip-usbdp.c b/drivers/phy/rockchip/phy-rockchip-usbdp.c
index 8874f8429a67..fa8324879a97 100644
--- a/drivers/phy/rockchip/phy-rockchip-usbdp.c
+++ b/drivers/phy/rockchip/phy-rockchip-usbdp.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2024 Collabora Ltd
  */
 
+#include <drm/bridge/aux-bridge.h>
 #include <dt-bindings/phy/phy.h>
 #include <linux/bitfield.h>
 #include <linux/bits.h>
@@ -1413,6 +1414,7 @@ static int rk_udphy_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct phy_provider *phy_provider;
+	struct fwnode_handle *dp_aux_ep;
 	struct resource *res;
 	struct rk_udphy *udphy;
 	void __iomem *base;
@@ -1467,6 +1469,21 @@ static int rk_udphy_probe(struct platform_device *pdev)
 			return ret;
 	}
 
+	/*
+	 * Only register the DRM bridge, if the DP aux channel is connected.
+	 * Some boards use the USBDP PHY only for its USB3 capabilities. The
+	 * aux bridge itself will be registered using port 0, endpoint 0, which
+	 * is fine as that is the actual superspeed data connection shared by
+	 * USB3 and DP based on the mux config.
+	 */
+	dp_aux_ep = fwnode_graph_get_endpoint_by_id(dev_fwnode(dev), 3, 0, 0);
+	if (dp_aux_ep) {
+		ret = drm_aux_bridge_register(dev);
+		fwnode_handle_put(dp_aux_ep);
+		if (ret)
+			return ret;
+	}
+
 	udphy->phy_u3 = devm_phy_create(dev, dev->of_node, &rk_udphy_usb3_phy_ops);
 	if (IS_ERR(udphy->phy_u3)) {
 		ret = PTR_ERR(udphy->phy_u3);

-- 
2.53.0