drivers: udc_dwc2: prevent access to registers if USBHS is not ready

On USBHS, we cannot access the DWC2 register until VBUS is detected and
valid. Kernel event API is used to block if a valid VBUS signal is not
present when the user tries to force usbd_enable().

Signed-off-by: Tomasz Moń <tomasz.mon@nordicsemi.no>
Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>

Author: jfischer-no

drivers/usb/udc/udc_dwc2_vendor_quirks.h

@@ -117,6 +117,15 @@ DT_INST_FOREACH_STATUS_OKAY(QUIRK_STM32F4_FSOTG_DEFINE)
 
 #define USBHS_DT_WRAPPER_REG_ADDR(n) UINT_TO_POINTER(DT_INST_REG_ADDR_BY_NAME(n, wrapper))
 
+/*
+ * On USBHS, we cannot access the DWC2 register until VBUS is detected and
+ * valid. If the user tries to force usbd_enable() and the corresponding
+ * udc_enable() without a "VBUS ready" notification, the event wait will block
+ * until a valid VBUS signal is detected.
+ */
+static K_EVENT_DEFINE(usbhs_events);
+#define USBHS_VBUS_READY	BIT(0)
+
 static void usbhs_vbus_handler(nrfs_usb_evt_t const *p_evt, void *const context)
 {
 	const struct device *dev = context;
@@ -127,8 +136,10 @@ static void usbhs_vbus_handler(nrfs_usb_evt_t const *p_evt, void *const context)
 			p_evt->usbhspll_ok, p_evt->vregusb_ok, p_evt->vbus_detected);
 
 		if (p_evt->usbhspll_ok && p_evt->vregusb_ok && p_evt->vbus_detected) {
+			k_event_post(&usbhs_events, USBHS_VBUS_READY);
 			udc_submit_event(dev, UDC_EVT_VBUS_READY, 0);
 		} else {
+			k_event_set_masked(&usbhs_events, 0, USBHS_VBUS_READY);
 			udc_submit_event(dev, UDC_EVT_VBUS_REMOVED, 0);
 		}
 
@@ -172,6 +183,11 @@ static inline int usbhs_enable_core(const struct device *dev)
 {
 	NRF_USBHS_Type *wrapper = USBHS_DT_WRAPPER_REG_ADDR(0);
 
+	if (!k_event_wait(&usbhs_events, USBHS_VBUS_READY, false, K_NO_WAIT)) {
+		LOG_WRN("VBUS is not ready, block udc_enable()");
+		k_event_wait(&usbhs_events, USBHS_VBUS_READY, false, K_FOREVER);
+	}
+
 	wrapper->ENABLE = USBHS_ENABLE_PHY_Msk | USBHS_ENABLE_CORE_Msk;
 	wrapper->TASKS_START = 1UL;