[PATCH 6/7] usb: dwc3: Add support for a role-switch notifier

["Bryan O'Donoghue" <bryan.odonoghue@xxxxxxxxxx>]

Role-switching is a 1:1 mapping between a producer and a consumer. For DWC3
we have some vendor specific wrappers, notably the qcom wrapper that want
to toggle some PHY related bits on a USB role switch.

This patch adds a role-switch notifier to the dwc3 drd code. When the USB
role-switch set() routine runs, the notifier will fire passing the notified
mode to the consumer, thus allowing vendor specific fix-ups to toggle from
the role-switching events.

Cc: Andy Gross <agross@xxxxxxxxxx>
Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Cc: Lee Jones <lee.jones@xxxxxxxxxx>
Cc: Felipe Balbi <balbi@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
Cc: Jack Pham <jackp@xxxxxxxxxxxxxx>
Cc: linux-arm-msm@xxxxxxxxxxxxxxx
Cc: linux-usb@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: Jack Pham <jackp@xxxxxxxxxxxxxx>
Tested-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
---
 drivers/usb/dwc3/core.h | 19 +++++++++++++++++++
 drivers/usb/dwc3/drd.c  | 17 +++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index a99e57636172..c2e85f587674 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -955,6 +955,7 @@ struct dwc3_scratchpad_array {
  *		- USBPHY_INTERFACE_MODE_UTMI
  *		- USBPHY_INTERFACE_MODE_UTMIW
  * @role_sw: usb_role_switch handle
+ * @role_sw_nl: role switch notifier list
  * @usb2_phy: pointer to USB2 PHY
  * @usb3_phy: pointer to USB3 PHY
  * @usb2_generic_phy: pointer to USB2 PHY
@@ -1089,6 +1090,7 @@ struct dwc3 {
 	struct notifier_block	edev_nb;
 	enum usb_phy_interface	hsphy_mode;
 	struct usb_role_switch	*role_sw;
+	struct raw_notifier_head role_sw_nl;
 
 	u32			fladj;
 	u32			irq_gadget;
@@ -1499,4 +1501,21 @@ static inline void dwc3_ulpi_exit(struct dwc3 *dwc)
 { }
 #endif
 
+#if IS_ENABLED(CONFIG_USB_ROLE_SWITCH)
+int dwc3_role_switch_notifier_register(struct dwc3 *dwc,
+				       struct notifier_block *nb);
+int dwc3_role_switch_notifier_unregister(struct dwc3 *dwc,
+					 struct notifier_block *nb);
+#else
+static inline int
+dwc3_role_switch_notifier_register(struct dwc3 *dwc,
+				   struct notifier_block *nb)
+{ return 0; }
+
+static inline int
+dwc3_role_switch_notifier_unregister(struct dwc3 *dwc,
+				     struct notifier_block *nb)
+{ return 0; }
+#endif
+
 #endif /* __DRIVERS_USB_DWC3_CORE_H */
diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index 2705871ec95e..789e93dd93b4 100644
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -497,6 +497,8 @@ static int dwc3_usb_role_switch_set(struct usb_role_switch *sw, enum usb_role ro
 	}
 
 	dwc3_set_mode(dwc, mode);
+	raw_notifier_call_chain(&dwc->role_sw_nl, mode, NULL);
+
 	return 0;
 }
 
@@ -560,6 +562,18 @@ static int dwc3_register_gpio_usb_connector(struct dwc3 *dwc)
 	return ret;
 }
 
+int dwc3_role_switch_notifier_register(struct dwc3 *dwc,
+				       struct notifier_block *nb)
+{
+	return raw_notifier_chain_register(&dwc->role_sw_nl, nb);
+}
+
+int dwc3_role_switch_notifier_unregister(struct dwc3 *dwc,
+					 struct notifier_block *nb)
+{
+	return raw_notifier_chain_unregister(&dwc->role_sw_nl, nb);
+}
+
 #else
 #define ROLE_SWITCH 0
 #define dwc3_setup_role_switch(x) 0
@@ -582,6 +596,9 @@ int dwc3_drd_init(struct dwc3 *dwc)
 		ret = dwc3_register_gpio_usb_connector(dwc);
 		if (ret < 0)
 			return ret;
+
+		RAW_INIT_NOTIFIER_HEAD(&dwc->role_sw_nl);
+
 	} else if (dwc->edev) {
 		dwc->edev_nb.notifier_call = dwc3_drd_notifier;
 		ret = extcon_register_notifier(dwc->edev, EXTCON_USB_HOST,
-- 
2.25.1