fix(rp2): process USB IN completions before OUT transfers

Without the mscStateStatusSent shortcut in the MSC state machine, the
CSW IN-completion must be observed before the next CBW OUT packet.
When both land in the same BUFF_STATUS snapshot the OUT-first loop
delivered the CBW while the state machine was still in StatusSent,
silently dropping it and wedging the host. Process IN completions
first, mirroring the nrf52840 EPDATA handler ordering.

Author: mikesmitty

src/machine/machine_rp2040_usb.go

@@ -92,21 +92,21 @@ func handleUSBIRQ(intr interrupt.Interrupt) {
 		s2 := rp.USBCTRL_REGS.BUFF_STATUS.Get()
 		rp.USBCTRL_REGS.BUFF_STATUS.Set(s2)
 
-		// OUT (PC -> rp2040)
+		// IN (rp2040 -> PC)
 		for i := 0; i < 16; i++ {
-			if s2&(1<<(i*2+1)) > 0 {
-				buf := handleEndpointRx(uint32(i))
-				if usbRxHandler[i] == nil || usbRxHandler[i](buf) {
-					AckUsbOutTransfer(uint32(i))
+			if s2&(1<<(i*2)) > 0 {
+				if usbTxHandler[i] != nil {
+					usbTxHandler[i]()
 				}
 			}
 		}
 
-		// IN (rp2040 -> PC)
+		// OUT (PC -> rp2040)
 		for i := 0; i < 16; i++ {
-			if s2&(1<<(i*2)) > 0 {
-				if usbTxHandler[i] != nil {
-					usbTxHandler[i]()
+			if s2&(1<<(i*2+1)) > 0 {
+				buf := handleEndpointRx(uint32(i))
+				if usbRxHandler[i] == nil || usbRxHandler[i](buf) {
+					AckUsbOutTransfer(uint32(i))
 				}
 			}
 		}

src/machine/machine_rp2350_usb.go

@@ -95,21 +95,21 @@ func handleUSBIRQ(intr interrupt.Interrupt) {
 		s2 := rp.USB.BUFF_STATUS.Get()
 		rp.USB.BUFF_STATUS.Set(s2)
 
-		// OUT (PC -> rp2350)
+		// IN (rp2350 -> PC)
 		for i := 0; i < 16; i++ {
-			if s2&(1<<(i*2+1)) > 0 {
-				buf := handleEndpointRx(uint32(i))
-				if usbRxHandler[i] == nil || usbRxHandler[i](buf) {
-					AckUsbOutTransfer(uint32(i))
+			if s2&(1<<(i*2)) > 0 {
+				if usbTxHandler[i] != nil {
+					usbTxHandler[i]()
 				}
 			}
 		}
 
-		// IN (rp2350 -> PC)
+		// OUT (PC -> rp2350)
 		for i := 0; i < 16; i++ {
-			if s2&(1<<(i*2)) > 0 {
-				if usbTxHandler[i] != nil {
-					usbTxHandler[i]()
+			if s2&(1<<(i*2+1)) > 0 {
+				buf := handleEndpointRx(uint32(i))
+				if usbRxHandler[i] == nil || usbRxHandler[i](buf) {
+					AckUsbOutTransfer(uint32(i))
 				}
 			}
 		}