[PATCH v2 6/8] 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 at quicinc.com>
Acked-by: Neil Armstrong <neil.armstrong at linaro.org>
Tested-by: Bryan O'Donoghue <bryan.odonoghue at linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue at linaro.org>
Tested-by: Abel Vesa <abel.vesa at linaro.org>
Tested-by: Steev Klimaszewski <steev at kali.org>
Tested-by: Neil Armstrong <neil.armstrong at linaro.org> # on HDK8450
Tested-by: Johan Hovold <johan+linaro at kernel.org>	# X13s
---

Changes since v1:
- Wrap DRM-related code in CONFIG_DRM guard
- Inroduce DRM-dependencies in Kconfig
- Dropped dev_err_probe() usage

 drivers/phy/qualcomm/Kconfig              |  2 +
 drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 46 +++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/drivers/phy/qualcomm/Kconfig b/drivers/phy/qualcomm/Kconfig
index 45330e0f66fe..67a45d95250d 100644
--- a/drivers/phy/qualcomm/Kconfig
+++ b/drivers/phy/qualcomm/Kconfig
@@ -60,8 +60,10 @@ config PHY_QCOM_QMP_COMBO
 	tristate "Qualcomm QMP Combo PHY Driver"
 	default PHY_QCOM_QMP
 	depends on TYPEC || TYPEC=n
+	depends on DRM || DRM=n
 	select GENERIC_PHY
 	select MFD_SYSCON
+	select DRM_PANEL_BRIDGE if DRM
 	help
 	  Enable this to support the QMP Combo PHY transceiver that is used
 	  with USB3 and DisplayPort controllers on Qualcomm chips.
diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-combo.c b/drivers/phy/qualcomm/phy-qcom-qmp-combo.c
index 52aa2735b841..d500cb8d2eec 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;
 };
@@ -3274,6 +3278,44 @@ static int qmp_combo_typec_switch_register(struct qmp_combo *qmp)
 }
 #endif
 
+#if IS_ENABLED(CONFIG_DRM)
+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)) {
+		dev_err(qmp->dev, "failed to acquire drm_bridge: %pe\n", next_bridge);
+		return PTR_ERR(next_bridge);
+	}
+
+	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);
+}
+#else
+static int qmp_combo_dp_register_bridge(struct qmp_combo *qmp)
+{
+	return 0;
+}
+#endif
+
 static int qmp_combo_parse_dt_lecacy_dp(struct qmp_combo *qmp, struct device_node *np)
 {
 	struct device *dev = qmp->dev;
@@ -3478,6 +3520,10 @@ 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