main: add callbacks for discrete USB states

We can save more power by parking threads when suspended, and threads should be deleted when disconnected. Also fix an inefficiency in usb_thread wakeups when the device is yet to be configured, but is addressed - slowing down control transfers. Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>

Author: P33M

src/main.c

@@ -75,8 +75,11 @@ void usb_thread(void *ptr)
  else
  gpio_put(PROBE_USB_CONNECTED_LED, 0);
 #endif
+ // If suspended or disconnected, delay for 1ms (20 ticks)
+ if (tud_suspended() || !tud_connected())
+ xTaskDelayUntil(&wake, 20);
  // Go to sleep for up to a tick if nothing to do
- if (!tud_task_event_ready())
+ else if (!tud_task_event_ready())
  xTaskDelayUntil(&wake, 1);
  } while (1);
 }
@@ -189,6 +192,40 @@ bool tud_vendor_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_requ
 }
 #endif
 
+void tud_suspend_cb(bool remote_wakeup_en)
+{
+ probe_info("Suspended\n");
+ /* Join DAP and UART threads? Or just suspend them, for transparency */
+ vTaskSuspend(uart_taskhandle);
+ vTaskSuspend(dap_taskhandle);
+ /* slow down clk_sys for power saving ? */
+}
+
+void tud_resume_cb(void)
+{
+ probe_info("Resumed\n");
+ vTaskResume(uart_taskhandle);
+ vTaskResume(dap_taskhandle);
+}
+
+void tud_unmount_cb(void)
+{
+ probe_info("Disconnected\n");
+ vTaskSuspend(uart_taskhandle);
+ vTaskSuspend(dap_taskhandle);
+ vTaskDelete(uart_taskhandle);
+ vTaskDelete(dap_taskhandle);
+}
+
+void tud_mount_cb(void)
+{
+ probe_info("Connected, Configured\n");
+ /* UART needs to preempt USB as if we don't, characters get lost */
+ xTaskCreate(cdc_thread, "UART", configMINIMAL_STACK_SIZE, NULL, UART_TASK_PRIO, &uart_taskhandle);
+ /* Lowest priority thread is debug - need to shuffle buffers before we can toggle swd... */
+ xTaskCreate(dap_thread, "DAP", configMINIMAL_STACK_SIZE, NULL, DAP_TASK_PRIO, &dap_taskhandle);
+}
+
 void vApplicationTickHook (void)
 {
 };