USBDevice: Add method to enable/disable phy

The new method can be call to disables the USB Phy to not block deep
sleep.

Author: hugueskamba

drivers/internal/USBDevice.h

@@ -256,6 +256,17 @@ class USBDevice: public  USBPhyEvents {
      */
     uint32_t write_finish(usb_ep_t endpoint);
 
+    /** Enable or disable phy
+     *
+     * Control enabling of device's phy. This is primarily intended
+     * for temporary power-saving; This call can
+     * allow usb to be temporarily disabled to permit power saving without
+     * losing device state.
+     *
+     *  @param enabled      true to enable, false to disable.
+     */
+    void enable_phy(bool enabled = true);
+
     /*
     * Get device descriptor.
     *
@@ -595,6 +606,7 @@ class USBDevice: public  USBPhyEvents {
     endpoint_info_t _endpoint_info[32 - 2];
 
     USBPhy *_phy;
+    bool _phy_enabled;
     bool _initialized;
     bool _connected;
     bool _endpoint_add_remove_allowed;

drivers/source/usb/USBDevice.cpp

@@ -1342,7 +1342,12 @@ void USBDevice::sof(int frame_number)
 }
 
 
-USBDevice::USBDevice(USBPhy *phy, uint16_t vendor_id, uint16_t product_id, uint16_t product_release)
+USBDevice::USBDevice(
+    USBPhy *phy,
+    uint16_t vendor_id,
+    uint16_t product_id,
+    uint16_t product_release
+) : _phy_enabled(true)
 {
     this->vendor_id = vendor_id;
     this->product_id = product_id;
@@ -1771,3 +1776,17 @@ void USBDevice::_run_later(void (USBDevice::*function)())
 {
     _post_process = function;
 }
+
+void USBDevice::enable_phy(bool enabled)
+{
+    core_util_critical_section_enter();
+    if (_phy_enabled != enabled) {
+        if (enabled) {
+            USBDevice::connect();
+        } else {
+            USBDevice::deinit();
+        }
+        _phy_enabled = enabled;
+    }
+    core_util_critical_section_exit();
+}