Add loopbackapp for app debugging using physical TKey with QEMU

This app takes data coming in on any of the normal USB endpoints
like CDC and FIDO (or CCID) and outputs the data on the DEBUG
endpoint.

Using the scripts (tkey_to_udp_linux.py, tkey_to_udp_win.py) in
QEMU (tk1 branch) under tools/tk1, the data from the DEBUG
endpoint can be read and sent over the network to the script
udp_to_qemu_linux.py that feeds it to QEMU.

hw/application_fpga/apps/Makefile

@@ -41,7 +41,7 @@ LDFLAGS = \
 	-L $(LIBDIR) -lcrt0 -lcommon -lmonocypher -lblake2s
 
 .PHONY: all
-all: defaultapp.bin reset_test.bin testapp.bin testloadapp.bin
+all: defaultapp.bin loopbackapp.bin reset_test.bin testapp.bin testloadapp.bin
 
 # Turn elf into bin for device
 %.bin: %.elf
@@ -66,6 +66,14 @@ DEFAULTAPP_OBJS = \
 defaultapp.elf: tkey-libs $(OBJS) $(DEFAULTAPP_OBJS)
 	$(CC) $(CFLAGS) $(OBJS) $(DEFAULTAPP_OBJS) $(LDFLAGS) -o $@
 
+# loopbackapp
+
+LOOPBACKAPP_OBJS = \
+	$(P)/loopbackapp/main.o
+
+loopbackapp.elf: tkey-libs $(LOOPBACKAPP_OBJS)
+	$(CC) $(CFLAGS) $(LOOPBACKAPP_OBJS) $(LDFLAGS) -o $@
+
 # reset_test
 
 RESET_TEST_FMTFILES = *.[ch]
@@ -97,6 +105,9 @@ fmt:
 	clang-format --dry-run --ferror-limit=0 defaultapp/*.[ch]
 	clang-format --verbose -i defaultapp/*.[ch]
 
+	clang-format --dry-run --ferror-limit=0 loopbackapp/*.[ch]
+	clang-format --verbose -i loopbackapp/*.[ch]
+
 	clang-format --dry-run --ferror-limit=0 reset_test/*.[ch]
 	clang-format --verbose -i reset_test/*.[ch]
 
@@ -110,6 +121,8 @@ fmt:
 checkfmt:
 	clang-format --dry-run --ferror-limit=0 defaultapp/*.[ch]
 
+	clang-format --dry-run --ferror-limit=0 loopbackapp/*.[ch]
+
 	clang-format --dry-run --ferror-limit=0 reset_test/*.[ch]
 
 	clang-format --dry-run --ferror-limit=0 testapp/*.[ch]
@@ -118,6 +131,6 @@ checkfmt:
 
 .PHONY: clean
 clean:
-	rm -f *.elf *.bin $(OBJS) $(DEFAULTAPP_OBJS) $(RESET_TEST_OBJS) \
-	$(TESTAPP_OBJS) $(TESTLOADAPP_OBJS)
+	rm -f *.elf *.bin $(OBJS) $(DEFAULTAPP_OBJS) $(LOOPBACKAPP_OBJS) \
+	$(RESET_TEST_OBJS) $(TESTAPP_OBJS) $(TESTLOADAPP_OBJS)
 

hw/application_fpga/apps/loopbackapp/main.c

@@ -0,0 +1,143 @@
+// Copyright (C) 2022, 2023 - Tillitis AB
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <tkey/assert.h>
+#include <tkey/io.h>
+#include <tkey/led.h>
+#include <tkey/lib.h>
+
+#define BUFSIZE 256
+#define HEADER_SIZE 2
+#define HID_PACKET_SIZE 64
+#define MAX_PAYLOAD_SIZE 64
+#define SLEEPTIME 100000
+
+void sleep(uint32_t n)
+{
+	for (volatile int i = 0; i < n; i++)
+		;
+}
+
+int main(void)
+{
+	uint8_t available = 0;
+	uint8_t cmdbuf[BUFSIZE] = {0};
+	enum ioend endpoint = IO_NONE;
+	bool waiting_for_more_data = false;
+	uint8_t dest_endpoint = IO_NONE;
+	uint8_t payload_length = 0;
+	uint8_t payload_left = 0;
+	uint8_t payloadbuf[MAX_PAYLOAD_SIZE] = {0};
+	uint8_t first_packet_len = HID_PACKET_SIZE - HEADER_SIZE;
+	uint8_t endpoints = IO_DEBUG;
+	led_set(LED_BLUE);
+
+	// Give time to CH552 to settle USB enumeration at power on
+	sleep(SLEEPTIME * 5);
+
+	// Setup available endpoints
+	endpoints |= IO_CDC | IO_FIDO;
+	config_endpoints(endpoints);
+
+	while (1) {
+		// Wait for data
+		if (readselect(endpoints, &endpoint, &available) != 0) {
+			assert(1 == 2);
+		}
+
+		switch (endpoint) {
+		case IO_CDC:
+			cmdbuf[0] = IO_CDC;
+			cmdbuf[1] = available;
+			if (read(IO_CDC, cmdbuf + 2, BUFSIZE - 2, available) <
+			    0) {
+				assert(1 == 2);
+			}
+			write(IO_DEBUG, cmdbuf, available + 2);
+			memset(cmdbuf, 0, BUFSIZE);
+			break;
+
+		case IO_FIDO:
+			cmdbuf[0] = IO_FIDO;
+			cmdbuf[1] = available;
+			if (read(IO_FIDO, cmdbuf + 2, BUFSIZE - 2, available) <
+			    0) {
+				assert(1 == 2);
+			}
+			write(IO_DEBUG, cmdbuf, available + 2);
+			memset(cmdbuf, 0, BUFSIZE);
+			break;
+
+		case IO_CCID:
+			cmdbuf[0] = IO_CCID;
+			cmdbuf[1] = available;
+			if (read(IO_CCID, cmdbuf + 2, BUFSIZE - 2, available) <
+			    0) {
+				assert(1 == 2);
+			}
+			write(IO_DEBUG, cmdbuf, available + 2);
+			memset(cmdbuf, 0, BUFSIZE);
+			break;
+
+		case IO_DEBUG:
+			if (available != HID_PACKET_SIZE) {
+				led_set(LED_RED);
+				while (1)
+					;
+			}
+
+			if (read(IO_DEBUG, cmdbuf, BUFSIZE, available) < 0) {
+				assert(1 == 2);
+			}
+
+			if (!waiting_for_more_data) {
+				dest_endpoint = cmdbuf[0];
+				payload_length = cmdbuf[1];
+
+				// Check that destination endpoint is ok
+				if (dest_endpoint != IO_CDC &&
+				    dest_endpoint != IO_FIDO &&
+				    dest_endpoint != IO_CCID) {
+					led_set(LED_RED);
+					while (1)
+						;
+				}
+
+				// Check payload size
+				if (payload_length > MAX_PAYLOAD_SIZE) {
+					led_set(LED_RED);
+					while (1)
+						;
+				}
+
+				// Complete payload fits in this packet
+				if (payload_length <= first_packet_len) {
+					write(dest_endpoint, cmdbuf + 2,
+					      payload_length);
+					memset(cmdbuf, 0, BUFSIZE);
+				} else { // More payload will come in next
+					 // packet
+					memcpy(payloadbuf, cmdbuf + 2,
+					       first_packet_len);
+					payload_left =
+					    payload_length - first_packet_len;
+					waiting_for_more_data = true;
+				}
+			} else {
+				memcpy(payloadbuf + first_packet_len, cmdbuf,
+				       payload_left);
+				write(dest_endpoint, payloadbuf,
+				      payload_length);
+				memset(payloadbuf, 0, MAX_PAYLOAD_SIZE);
+				memset(cmdbuf, 0, BUFSIZE);
+				waiting_for_more_data = false;
+			}
+			break;
+
+		default:
+			break;
+		}
+	}
+}