Teensy 4.1: implement USB remote wakeup

This allows waking up a computer from Suspend-to-RAM by pressing a key on the
keyboard (with the QMK keyboard firmware, which uses ChibiOS for the Teensy).

Author: stapelberg

ext/nxp-middleware-usb/device/usb_device_ehci.c

@@ -1555,6 +1555,13 @@ usb_status_t USB_DeviceEhciCancel(usb_device_controller_handle ehciHandle, uint8
     return kStatus_USB_Success;
 }
 
+static uint32_t ms_to_cycles(const uint32_t val) {
+  // 600 cycles at 0.6 cycles/ns == 1μs
+  const uint32_t cycles_per_us = 600;
+  const uint32_t ms_to_us = 1000;
+  return val * ms_to_us * cycles_per_us;
+}
+
 /*!
  * @brief Control the status of the selected item.
  *
@@ -1696,8 +1703,11 @@ usb_status_t USB_DeviceEhciControl(usb_device_controller_handle ehciHandle, usb_
 #endif
             ehciState->registerBase->PORTSC1 &= ~USBHS_PORTSC1_PHCD_MASK;
             ehciState->registerBase->PORTSC1 |= USBHS_PORTSC1_FPR_MASK;
-            startTick = deviceHandle->hwTick;
-            while ((deviceHandle->hwTick - startTick) < 10U)
+            // For easier ChibiOS integration, directly query the (already
+            // enabled) CYCCNT register instead of the deviceHandle->hwTick
+            // variable, which ChibiOS currently does not update.
+            startTick = DWT->CYCCNT;
+            while ((DWT->CYCCNT - startTick) < ms_to_cycles(10U))
             {
                 __NOP();
             }

os/hal/ports/MIMXRT1062/LLD/USBHSv1/hal_usb_lld.c

@@ -116,12 +116,16 @@ static usb_status_t usb_device_callback(usb_device_handle handle, uint32_t callb
     break;
 
   case kUSB_DeviceEventSuspend:
-    printf_debug("  suspend");
+    printf_debug("  suspend--nxp");
+    // Call USB_DeviceSetStatus() to enable the “detect resume” interrupt.
+    usb_device_struct_t *dev_handle = (usb_device_struct_t *)handle;
+    (void)USB_DeviceSetStatus(dev_handle, kUSB_DeviceStatusBusSuspend, NULL);
+    printf_debug("  suspend--chibi");
     _usb_suspend(usbp);
     break;
 
   case kUSB_DeviceEventResume:
-    printf_debug("  resume");
+    printf_debug("  resume--chibi");
     _usb_wakeup(usbp);
     break;
   }

os/hal/ports/MIMXRT1062/LLD/USBHSv1/hal_usb_lld.h

@@ -408,8 +408,10 @@ struct USBDriver {
  * @notapi
  */
 #define usb_lld_wakeup_host(usbp)                                     \
-  do{                                                                 \
-  } while (false)
+  do{ \
+    usb_device_struct_t *dev_handle = (usb_device_struct_t *)handle; \
+    (void)USB_DeviceSetStatus(dev_handle, kUSB_DeviceStatusBusResume, NULL); \
+  } while (0)
 
 
 /*===========================================================================*/

os/hal/ports/MIMXRT1062/LLD/USBHSv1/usb_device_config.h

@@ -154,11 +154,11 @@
 #define USB_DEVICE_CONFIG_BUFFER_PROPERTY_CACHEABLE (0U)
 #endif
 /*! @brief Whether the low power mode is enabled or not. */
-#define USB_DEVICE_CONFIG_LOW_POWER_MODE (0U)
+#define USB_DEVICE_CONFIG_LOW_POWER_MODE (1U)
 
 #if ((defined(USB_DEVICE_CONFIG_LOW_POWER_MODE)) && (USB_DEVICE_CONFIG_LOW_POWER_MODE > 0U))
 /*! @brief Whether device remote wakeup supported. 1U supported, 0U not supported */
-#define USB_DEVICE_CONFIG_REMOTE_WAKEUP (0U)
+#define USB_DEVICE_CONFIG_REMOTE_WAKEUP (1U)
 
 /*! @brief Whether LPM is supported. 1U supported, 0U not supported */
 #define USB_DEVICE_CONFIG_LPM_L1 (0U)