samd: Switch TinyUSB to run via a scheduled task.

Previously the TinyUSB task was run in the ISR immediately after the
interrupt handler.  This approach gives very similar performance (no change
in CDC throughput tests) but reduces the amount of time spent in the ISR,
and allows TinyUSB callbacks to run in thread mode.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

ports/samd/Makefile

@@ -93,6 +93,8 @@ LIBSTDCPP_FILE_NAME = "$(shell $(CXX) $(CXXFLAGS) -print-file-name=libstdc++.a)"
 LDFLAGS += -L"$(shell dirname $(LIBSTDCPP_FILE_NAME))"
 endif
 
+LDFLAGS += --wrap=dcd_event_handler
+
 MPY_CROSS_FLAGS += -march=$(MPY_CROSS_MCU_ARCH)
 
 SRC_C += \
@@ -131,6 +133,7 @@ SHARED_SRC_C += \
 	shared/runtime/sys_stdio_mphal.c \
 	shared/timeutils/timeutils.c \
 	shared/tinyusb/mp_cdc_common.c \
+	shared/tinyusb/mp_usbd.c
 
 ASF4_SRC_C += $(addprefix lib/asf4/$(MCU_SERIES_LOWER)/,\
 	hal/src/hal_atomic.c \

ports/samd/samd_isr.c

@@ -310,10 +310,10 @@ const ISR isr_vector[] __attribute__((section(".isr_vector"))) = {
     &Sercom7_Handler, // 77 Serial Communication Interface 7 (SERCOM7): SERCOM7_3 - 6
     0,                // 78 Control Area Network 0 (CAN0)
     0,                // 79 Control Area Network 1 (CAN1)
-    &USB_0_Handler_wrapper, // 80 Universal Serial Bus (USB): USB_EORSM_DNRS, ...
-    &USB_1_Handler_wrapper, // 81 Universal Serial Bus (USB): USB_SOF_HSOF
-    &USB_2_Handler_wrapper, // 82 Universal Serial Bus (USB): USB_TRCPT0_0 - _7
-    &USB_3_Handler_wrapper, // 83 Universal Serial Bus (USB): USB_TRCPT1_0 - _7
+    &USB_Handler_wrapper, // 80 Universal Serial Bus (USB): USB_EORSM_DNRS, ...
+    &USB_Handler_wrapper, // 81 Universal Serial Bus (USB): USB_SOF_HSOF
+    &USB_Handler_wrapper, // 82 Universal Serial Bus (USB): USB_TRCPT0_0 - _7
+    &USB_Handler_wrapper, // 83 Universal Serial Bus (USB): USB_TRCPT1_0 - _7
     0,                // 84 Ethernet MAC (GMAC)
     0,                // 85 Timer Counter Control 0 (TCC0): TCC0_CNT_A ...
     0,                // 86 Timer Counter Control 0 (TCC0): TCC0_MC_0

ports/samd/samd_soc.h

@@ -36,10 +36,6 @@ void samd_init(void);
 void samd_main(void);
 
 void USB_Handler_wrapper(void);
-void USB_0_Handler_wrapper(void);
-void USB_1_Handler_wrapper(void);
-void USB_2_Handler_wrapper(void);
-void USB_3_Handler_wrapper(void);
 
 void sercom_enable(Sercom *spi, int state);
 void sercom_register_irq(int sercom_id, void (*sercom_irq_handler));

ports/samd/tusb_port.c

@@ -117,33 +117,6 @@ const uint16_t *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
     return desc_str;
 }
 
-#if defined(MCU_SAMD21)
-
 void USB_Handler_wrapper(void) {
     tud_int_handler(0);
-    tud_task();
-}
-
-#elif defined(MCU_SAMD51)
-
-void USB_0_Handler_wrapper(void) {
-    tud_int_handler(0);
-    tud_task();
-}
-
-void USB_1_Handler_wrapper(void) {
-    tud_int_handler(0);
-    tud_task();
 }
-
-void USB_2_Handler_wrapper(void) {
-    tud_int_handler(0);
-    tud_task();
-}
-
-void USB_3_Handler_wrapper(void) {
-    tud_int_handler(0);
-    tud_task();
-}
-
-#endif