plat/st/common/stm32cubeprogrammer_uart.c - trusted-firmware-a - Git at Google

 /*
  * Copyright (c) 2021-2023, STMicroelectronics - All Rights Reserved
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */

 #include <assert.h>
 #include <endian.h>
 #include <errno.h>
 #include <string.h>

 #include <arch_helpers.h>
 #include <common/debug.h>
 #include <drivers/delay_timer.h>
 #include <drivers/st/stm32_iwdg.h>
 #include <drivers/st/stm32_uart.h>
 #include <drivers/st/stm32_uart_regs.h>
 #include <lib/mmio.h>
 #include <tools_share/firmware_image_package.h>

 #include <platform_def.h>
 #include <stm32cubeprogrammer.h>

 /* USART bootloader protocol version V4.0 */
 #define USART_BL_VERSION	0x40U

 /* Command definition */
 #define GET_CMD_COMMAND		0x00U
 #define GET_VER_COMMAND		0x01U
 #define GET_ID_COMMAND		0x02U
 #define PHASE_COMMAND		0x03U
 #define READ_PART_COMMAND	0x12U
 #define START_COMMAND		0x21U
 #define DOWNLOAD_COMMAND	0x31U

 /* Answer defines */
 #define INIT_BYTE		0x7FU
 #define ACK_BYTE		0x79U
 #define NACK_BYTE		0x1FU
 #define ABORT			0x5FU

 #define UNDEFINED_DOWN_ADDR	U(0xFFFFFFFF)
 #define PROGRAMMER_TIMEOUT_US	20000U

 static const uint8_t command_tab[] = {
 	GET_CMD_COMMAND,
 	GET_VER_COMMAND,
 	GET_ID_COMMAND,
 	PHASE_COMMAND,
 	START_COMMAND,
 	DOWNLOAD_COMMAND
 };

 /* STM32CubeProgrammer over UART handle */
 struct stm32prog_uart_handle_s {
 	struct stm32_uart_handle_s uart;
 	uint32_t packet;
 	uint8_t *addr;
 	uint32_t len;
 	uint8_t phase;
 	/* Error msg buffer: max 255 in UART protocol, reduced in TF-A */
 	uint8_t error[64];
 } handle;

 /* Trace and handle unrecoverable UART protocol error */
 #define STM32PROG_ERROR(...) \
 	{ \
 		ERROR(__VA_ARGS__); \
 		if (handle.phase != PHASE_RESET) { \
 			snprintf((char *)&handle.error, sizeof(handle.error), __VA_ARGS__); \
 			handle.phase = PHASE_RESET; \
 			handle.addr = (uint8_t *)UNDEFINED_DOWN_ADDR; \
 			handle.len = 0U; \
 			handle.packet = 0U; \
 		} \
 	}

 static int uart_write(const uint8_t *addr, uint16_t size)
 {
 	while (size != 0U) {
 		if (stm32_uart_putc(&handle.uart, *addr) != 0) {
 			return -EIO;
 		}
 		size--;
 		addr++;
 	}

 	return 0;
 }

 static int uart_write_8(uint8_t byte)
 {
 	return stm32_uart_putc(&handle.uart, byte);
 }

 static int uart_write_32(uint32_t value)
 {
 	return uart_write((uint8_t *)&value, 4U);
 }

 static int uart_read_8(uint8_t *byte)
 {
 	int ret;
 	uint64_t timeout_ref = timeout_init_us(PROGRAMMER_TIMEOUT_US);

 	do {
 		ret = stm32_uart_getc(&handle.uart);
 		if (ret == -EAGAIN) {
 			if (timeout_elapsed(timeout_ref)) {
 				return -ETIMEDOUT;
 			}
 		} else if (ret < 0) {
 			return ret;
 		}
 	} while (ret == -EAGAIN);

 	*byte = (uint8_t)ret;

 	return 0;
 }

 static int uart_send_result(uint8_t byte)
 {
 	int ret;

 	/* Always flush fifo before to send result = read all pending data */
 	do {
 		ret = stm32_uart_getc(&handle.uart);
 	} while (ret >= 0);

 	return uart_write_8(byte);
 }

 static bool is_valid_header(fip_toc_header_t *header)
 {
 	return (header->name == TOC_HEADER_NAME) &&
 	       (header->serial_number != 0U);
 }

 static int uart_receive_command(uint8_t *command)
 {
 	uint8_t byte = 0U;
 	uint8_t xor = 0U;
 	unsigned int count;
 	bool found = false;
 	int ret;

 	/* Repeat read until something is received */
 	do {
 		stm32_iwdg_refresh();
 		ret = uart_read_8(&byte);
 	} while (ret == -ETIMEDOUT);

 	if (ret != 0) {
 		return ret;
 	}

 	/* Handle reconnection request */
 	if (byte == INIT_BYTE) {
 		*command = byte;
 		return 0;
 	}

 	for (count = 0U; count < ARRAY_SIZE(command_tab); count++) {
 		if (command_tab[count] == byte) {
 			found = true;
 			break;
 		}
 	}
 	if (!found) {
 		VERBOSE("UART: Command unknown (byte=0x%x)\n", byte);
 		return -EPROTO;
 	}

 	ret = uart_read_8(&xor);
 	if (ret != 0) {
 		return ret;
 	}
 	if ((byte ^ xor) != 0xFF) {
 		VERBOSE("UART: Command XOR check fail (byte=0x%x, xor=0x%x)\n",
 			byte, xor);
 		return -EPROTO;
 	}

 	*command = byte;

 	return 0;
 }

 static int get_cmd_command(void)
 {
 	const uint8_t msg[2] = {
 		sizeof(command_tab), /* Length of data - 1 */
 		USART_BL_VERSION
 	};
 	int ret;

 	ret = uart_write(msg, sizeof(msg));
 	if (ret != 0) {
 		return ret;
 	}

 	return uart_write(command_tab, sizeof(command_tab));
 }

 static int get_version_command(void)
 {
 	return uart_write_8(STM32_TF_VERSION);
 }

 static int get_id_command(void)
 {
 	uint8_t msg[3] = {
 		sizeof(msg) - 1 /* Length of data - 1 */
 	};
 	uint32_t chip_id = stm32mp_get_chip_dev_id();

 	be16enc(&msg[1], chip_id);

 	return uart_write(msg, sizeof(msg));
 }

 static int uart_send_phase(uint32_t address)
 {
 	int ret;
 	uint8_t msg_size = 5U; /* Length of data - 1 */
 	uint8_t error_size = 0U;

 	/* Additional information only for RESET phase */
 	if (handle.phase == PHASE_RESET) {
 		error_size = strnlen((char *)&handle.error, sizeof(handle.error));
 	}
 	ret = uart_write_8(msg_size + error_size);
 	if (ret != 0) {
 		return ret;
 	}

 	/* Send the ID of next partition */
 	ret = uart_write_8(handle.phase);
 	if (ret != 0) {
 		return ret;
 	}

 	/* Destination address */
 	ret = uart_write_32(address);
 	if (ret != 0) {
 		return ret;
 	}

 	ret = uart_write_8(error_size);
 	if (ret != 0) {
 		return ret;
 	}

 	/* Additional information: message error */
 	if (error_size > 0U) {
 		ret = uart_write(handle.error, error_size);
 	}

 	return ret;
 }

 static int uart_download_part(void)
 {
 	uint8_t operation = 0U;
 	uint8_t xor;
 	uint8_t byte = 0U;
 	uint32_t packet_number = 0U;
 	uint32_t packet_size = 0U;
 	uint32_t i = 0U;
 	int ret;

 	/* Get operation number */
 	ret = uart_read_8(&operation);
 	if (ret != 0) {
 		return ret;
 	}

 	xor = operation;

 	/* Get packet number */
 	for (i = 3U; i != 0U; i--) {
 		ret = uart_read_8(&byte);
 		if (ret != 0) {
 			return ret;
 		}

 		xor ^= byte;
 		packet_number = (packet_number << 8) | byte;
 	}

 	if (packet_number != handle.packet) {
 		WARN("UART: Bad packet number receive: %u, expected %u\n",
 		     packet_number, handle.packet);
 		return -EPROTO;
 	}

 	/* Checksum */
 	ret = uart_read_8(&byte);
 	if (ret != 0) {
 		return ret;
 	}
 	if (xor != byte) {
 		VERBOSE("UART: Download Command checksum xor: %x, received %x\n",
 			xor, byte);
 		return -EPROTO;
 	}

 	ret = uart_send_result(ACK_BYTE);
 	if (ret != 0) {
 		return ret;
 	}

 	ret = uart_read_8(&byte);
 	if (ret != 0) {
 		return ret;
 	}
 	xor = byte;
 	packet_size = byte + 1U;
 	if (handle.len < packet_size) {
 		STM32PROG_ERROR("Download overflow at %p\n", handle.addr + packet_size);
 		return 0;
 	}

 	for (i = 0U; i < packet_size; i++) {
 		ret = uart_read_8(&byte);
 		if (ret != 0) {
 			return ret;
 		}

 		*(handle.addr + i) = byte;
 		xor ^= byte;
 	}

 	/* Checksum */
 	ret = uart_read_8(&byte) != 0;
 	if (ret != 0) {
 		return ret;
 	}
 	if (xor != byte) {
 		VERBOSE("UART: Download Data checksum xor: %x, received %x\n",
 			xor, byte);
 		return -EPROTO;
 	}

 	/* Packet treated */
 	handle.packet++;
 	handle.addr += packet_size;
 	handle.len -= packet_size;

 	return 0;
 }

 static int uart_start_cmd(uintptr_t buffer)
 {
 	uint8_t byte = 0U;
 	uint8_t xor = 0U;
 	uint32_t i;
 	uint32_t start_address = 0U;
 	int ret;

 	/* Get address */
 	for (i = 4U; i != 0U; i--) {
 		ret = uart_read_8(&byte);
 		if (ret != 0U) {
 			return ret;
 		}

 		xor ^= byte;
 		start_address = (start_address << 8) | byte;
 	}

 	/* Checksum */
 	ret = uart_read_8(&byte);
 	if (ret != 0) {
 		return ret;
 	}

 	if (xor != byte) {
 		VERBOSE("UART: Start Command checksum xor: %x, received %x\n",
 			xor, byte);
 		return -EPROTO;
 	}

 	if (start_address != UNDEFINED_DOWN_ADDR) {
 		STM32PROG_ERROR("Invalid start at %x, for phase %u\n",
 				start_address, handle.phase);
 		return 0;
 	}

 	if (!is_valid_header((fip_toc_header_t *)buffer)) {
 		STM32PROG_ERROR("FIP Header check failed %lx, for phase %u\n",
 				buffer, handle.phase);
 		return -EIO;
 	}
 	VERBOSE("FIP header looks OK.\n");

 	return 0;
 }

 static int uart_read(uint8_t id, uintptr_t buffer, size_t length)
 {
 	bool start_done = false;
 	int ret;
 	uint8_t command = 0U;

 	handle.phase = id;
 	handle.packet = 0U;
 	handle.addr = (uint8_t *)buffer;
 	handle.len = length;

 	INFO("UART: read phase %u at 0x%lx size 0x%zx\n",
 	     id, buffer, length);
 	while (!start_done) {
 		ret = uart_receive_command(&command);
 		if (ret != 0) {
 			/* Delay to wait STM32CubeProgrammer end of transmission */
 			mdelay(3);

 			ret = uart_send_result(NACK_BYTE);
 			if (ret != 0U) {
 				return ret;
 			}

 			continue;
 		}

 		uart_send_result(ACK_BYTE);

 		switch (command) {
 		case INIT_BYTE:
 			INFO("UART: Connected\n");
 			/* Nothing to do */
 			continue;

 		case GET_CMD_COMMAND:
 			ret = get_cmd_command();
 			break;

 		case GET_VER_COMMAND:
 			ret = get_version_command();
 			break;

 		case GET_ID_COMMAND:
 			ret = get_id_command();
 			break;

 		case PHASE_COMMAND:
 			ret = uart_send_phase((uint32_t)buffer);
 			if ((ret == 0) && (handle.phase == PHASE_RESET)) {
 				start_done = true;
 				INFO("UART: Reset\n");
 			}
 			break;

 		case DOWNLOAD_COMMAND:
 			ret = uart_download_part();
 			break;

 		case START_COMMAND:
 			ret = uart_start_cmd(buffer);
 			if ((ret == 0) && (handle.phase == id)) {
 				INFO("UART: Start phase %u\n", handle.phase);
 				start_done = true;
 			}
 			break;

 		default:
 			WARN("UART: Unknown command\n");
 			ret = -EINVAL;
 			break;
 		}

 		if (ret == 0) {
 			ret = uart_send_result(ACK_BYTE);
 		} else {
 			ret = uart_send_result(NACK_BYTE);
 		}
 		if (ret != 0) {
 			return ret;
 		}
 	}

 	stm32_uart_flush(&handle.uart);

 	return 0;
 }

 /* Init UART: 115200, 8bit 1stop parity even and enable FIFO mode */
 const struct stm32_uart_init_s init = {
 	.baud_rate = STM32MP_UART_BAUDRATE,
 	.word_length = STM32_UART_WORDLENGTH_9B,
 	.stop_bits = STM32_UART_STOPBITS_1,
 	.parity = STM32_UART_PARITY_EVEN,
 	.hw_flow_control = STM32_UART_HWCONTROL_NONE,
 	.mode = STM32_UART_MODE_TX_RX,
 	.fifo_mode = STM32_UART_FIFOMODE_EN,
 };

 int stm32cubeprog_uart_load(uintptr_t instance, uintptr_t base, size_t len)
 {
 	int ret;

 	if (stm32_uart_init(&handle.uart, instance, &init) != 0) {
 		return -EIO;
 	}

 	/*
 	 * The following NACK_BYTE is written because STM32CubeProgrammer has
 	 * already sent its command before TF-A has reached this point, and
 	 * because FIFO was not configured by BootROM.
 	 * The byte in the UART_RX register is then the checksum and not the
 	 * command. NACK_BYTE has to be written, so that the programmer will
 	 * re-send the good command.
 	 */
 	ret = uart_send_result(NACK_BYTE);
 	if (ret != 0) {
 		return ret;
 	}

 	return uart_read(PHASE_SSBL, base, len);
 }
	/*
	* Copyright (c) 2021-2023, STMicroelectronics - All Rights Reserved
	*
	* SPDX-License-Identifier: BSD-3-Clause
	*/

	#include <assert.h>
	#include <endian.h>
	#include <errno.h>
	#include <string.h>

	#include <arch_helpers.h>
	#include <common/debug.h>
	#include <drivers/delay_timer.h>
	#include <drivers/st/stm32_iwdg.h>
	#include <drivers/st/stm32_uart.h>
	#include <drivers/st/stm32_uart_regs.h>
	#include <lib/mmio.h>
	#include <tools_share/firmware_image_package.h>

	#include <platform_def.h>
	#include <stm32cubeprogrammer.h>

	/* USART bootloader protocol version V4.0 */
	#define USART_BL_VERSION 0x40U

	/* Command definition */
	#define GET_CMD_COMMAND 0x00U
	#define GET_VER_COMMAND 0x01U
	#define GET_ID_COMMAND 0x02U
	#define PHASE_COMMAND 0x03U
	#define READ_PART_COMMAND 0x12U
	#define START_COMMAND 0x21U
	#define DOWNLOAD_COMMAND 0x31U

	/* Answer defines */
	#define INIT_BYTE 0x7FU
	#define ACK_BYTE 0x79U
	#define NACK_BYTE 0x1FU
	#define ABORT 0x5FU

	#define UNDEFINED_DOWN_ADDR U(0xFFFFFFFF)
	#define PROGRAMMER_TIMEOUT_US 20000U

	static const uint8_t command_tab[] = {
	GET_CMD_COMMAND,
	GET_VER_COMMAND,
	GET_ID_COMMAND,
	PHASE_COMMAND,
	START_COMMAND,
	DOWNLOAD_COMMAND
	};

	/* STM32CubeProgrammer over UART handle */
	struct stm32prog_uart_handle_s {
	struct stm32_uart_handle_s uart;
	uint32_t packet;
	uint8_t *addr;
	uint32_t len;
	uint8_t phase;
	/* Error msg buffer: max 255 in UART protocol, reduced in TF-A */
	uint8_t error[64];
	} handle;

	/* Trace and handle unrecoverable UART protocol error */
	#define STM32PROG_ERROR(...) \
	{ \
	ERROR(__VA_ARGS__); \
	if (handle.phase != PHASE_RESET) { \
	snprintf((char *)&handle.error, sizeof(handle.error), __VA_ARGS__); \
	handle.phase = PHASE_RESET; \
	handle.addr = (uint8_t *)UNDEFINED_DOWN_ADDR; \
	handle.len = 0U; \
	handle.packet = 0U; \
	} \
	}

	static int uart_write(const uint8_t *addr, uint16_t size)
	{
	while (size != 0U) {
	if (stm32_uart_putc(&handle.uart, *addr) != 0) {
	return -EIO;
	}
	size--;
	addr++;
	}

	return 0;
	}

	static int uart_write_8(uint8_t byte)
	{
	return stm32_uart_putc(&handle.uart, byte);
	}

	static int uart_write_32(uint32_t value)
	{
	return uart_write((uint8_t *)&value, 4U);
	}

	static int uart_read_8(uint8_t *byte)
	{
	int ret;
	uint64_t timeout_ref = timeout_init_us(PROGRAMMER_TIMEOUT_US);

	do {
	ret = stm32_uart_getc(&handle.uart);
	if (ret == -EAGAIN) {
	if (timeout_elapsed(timeout_ref)) {
	return -ETIMEDOUT;
	}
	} else if (ret < 0) {
	return ret;
	}
	} while (ret == -EAGAIN);

	*byte = (uint8_t)ret;

	return 0;
	}

	static int uart_send_result(uint8_t byte)
	{
	int ret;

	/* Always flush fifo before to send result = read all pending data */
	do {
	ret = stm32_uart_getc(&handle.uart);
	} while (ret >= 0);

	return uart_write_8(byte);
	}

	static bool is_valid_header(fip_toc_header_t *header)
	{
	return (header->name == TOC_HEADER_NAME) &&
	(header->serial_number != 0U);
	}

	static int uart_receive_command(uint8_t *command)
	{
	uint8_t byte = 0U;
	uint8_t xor = 0U;
	unsigned int count;
	bool found = false;
	int ret;

	/* Repeat read until something is received */
	do {
	stm32_iwdg_refresh();
	ret = uart_read_8(&byte);
	} while (ret == -ETIMEDOUT);

	if (ret != 0) {
	return ret;
	}

	/* Handle reconnection request */
	if (byte == INIT_BYTE) {
	*command = byte;
	return 0;
	}

	for (count = 0U; count < ARRAY_SIZE(command_tab); count++) {
	if (command_tab[count] == byte) {
	found = true;
	break;
	}
	}
	if (!found) {
	VERBOSE("UART: Command unknown (byte=0x%x)\n", byte);
	return -EPROTO;
	}

	ret = uart_read_8(&xor);
	if (ret != 0) {
	return ret;
	}
	if ((byte ^ xor) != 0xFF) {
	VERBOSE("UART: Command XOR check fail (byte=0x%x, xor=0x%x)\n",
	byte, xor);
	return -EPROTO;
	}

	*command = byte;

	return 0;
	}

	static int get_cmd_command(void)
	{
	const uint8_t msg[2] = {
	sizeof(command_tab), /* Length of data - 1 */
	USART_BL_VERSION
	};
	int ret;

	ret = uart_write(msg, sizeof(msg));
	if (ret != 0) {
	return ret;
	}

	return uart_write(command_tab, sizeof(command_tab));
	}

	static int get_version_command(void)
	{
	return uart_write_8(STM32_TF_VERSION);
	}

	static int get_id_command(void)
	{
	uint8_t msg[3] = {
	sizeof(msg) - 1 /* Length of data - 1 */
	};
	uint32_t chip_id = stm32mp_get_chip_dev_id();

	be16enc(&msg[1], chip_id);

	return uart_write(msg, sizeof(msg));
	}

	static int uart_send_phase(uint32_t address)
	{
	int ret;
	uint8_t msg_size = 5U; /* Length of data - 1 */
	uint8_t error_size = 0U;

	/* Additional information only for RESET phase */
	if (handle.phase == PHASE_RESET) {
	error_size = strnlen((char *)&handle.error, sizeof(handle.error));
	}
	ret = uart_write_8(msg_size + error_size);
	if (ret != 0) {
	return ret;
	}

	/* Send the ID of next partition */
	ret = uart_write_8(handle.phase);
	if (ret != 0) {
	return ret;
	}

	/* Destination address */
	ret = uart_write_32(address);
	if (ret != 0) {
	return ret;
	}

	ret = uart_write_8(error_size);
	if (ret != 0) {
	return ret;
	}

	/* Additional information: message error */
	if (error_size > 0U) {
	ret = uart_write(handle.error, error_size);
	}

	return ret;
	}

	static int uart_download_part(void)
	{
	uint8_t operation = 0U;
	uint8_t xor;
	uint8_t byte = 0U;
	uint32_t packet_number = 0U;
	uint32_t packet_size = 0U;
	uint32_t i = 0U;
	int ret;

	/* Get operation number */
	ret = uart_read_8(&operation);
	if (ret != 0) {
	return ret;
	}

	xor = operation;

	/* Get packet number */
	for (i = 3U; i != 0U; i--) {
	ret = uart_read_8(&byte);
	if (ret != 0) {
	return ret;
	}

	xor ^= byte;
	packet_number = (packet_number << 8) \| byte;
	}

	if (packet_number != handle.packet) {
	WARN("UART: Bad packet number receive: %u, expected %u\n",
	packet_number, handle.packet);
	return -EPROTO;
	}

	/* Checksum */
	ret = uart_read_8(&byte);
	if (ret != 0) {
	return ret;
	}
	if (xor != byte) {
	VERBOSE("UART: Download Command checksum xor: %x, received %x\n",
	xor, byte);
	return -EPROTO;
	}

	ret = uart_send_result(ACK_BYTE);
	if (ret != 0) {
	return ret;
	}

	ret = uart_read_8(&byte);
	if (ret != 0) {
	return ret;
	}
	xor = byte;
	packet_size = byte + 1U;
	if (handle.len < packet_size) {
	STM32PROG_ERROR("Download overflow at %p\n", handle.addr + packet_size);
	return 0;
	}

	for (i = 0U; i < packet_size; i++) {
	ret = uart_read_8(&byte);
	if (ret != 0) {
	return ret;
	}

	*(handle.addr + i) = byte;
	xor ^= byte;
	}

	/* Checksum */
	ret = uart_read_8(&byte) != 0;
	if (ret != 0) {
	return ret;
	}
	if (xor != byte) {
	VERBOSE("UART: Download Data checksum xor: %x, received %x\n",
	xor, byte);
	return -EPROTO;
	}

	/* Packet treated */
	handle.packet++;
	handle.addr += packet_size;
	handle.len -= packet_size;

	return 0;
	}

	static int uart_start_cmd(uintptr_t buffer)
	{
	uint8_t byte = 0U;
	uint8_t xor = 0U;
	uint32_t i;
	uint32_t start_address = 0U;
	int ret;

	/* Get address */
	for (i = 4U; i != 0U; i--) {
	ret = uart_read_8(&byte);
	if (ret != 0U) {
	return ret;
	}

	xor ^= byte;
	start_address = (start_address << 8) \| byte;
	}

	/* Checksum */
	ret = uart_read_8(&byte);
	if (ret != 0) {
	return ret;
	}

	if (xor != byte) {
	VERBOSE("UART: Start Command checksum xor: %x, received %x\n",
	xor, byte);
	return -EPROTO;
	}

	if (start_address != UNDEFINED_DOWN_ADDR) {
	STM32PROG_ERROR("Invalid start at %x, for phase %u\n",
	start_address, handle.phase);
	return 0;
	}

	if (!is_valid_header((fip_toc_header_t *)buffer)) {
	STM32PROG_ERROR("FIP Header check failed %lx, for phase %u\n",
	buffer, handle.phase);
	return -EIO;
	}
	VERBOSE("FIP header looks OK.\n");

	return 0;
	}

	static int uart_read(uint8_t id, uintptr_t buffer, size_t length)
	{
	bool start_done = false;
	int ret;
	uint8_t command = 0U;

	handle.phase = id;
	handle.packet = 0U;
	handle.addr = (uint8_t *)buffer;
	handle.len = length;

	INFO("UART: read phase %u at 0x%lx size 0x%zx\n",
	id, buffer, length);
	while (!start_done) {
	ret = uart_receive_command(&command);
	if (ret != 0) {
	/* Delay to wait STM32CubeProgrammer end of transmission */
	mdelay(3);

	ret = uart_send_result(NACK_BYTE);
	if (ret != 0U) {
	return ret;
	}

	continue;
	}

	uart_send_result(ACK_BYTE);

	switch (command) {
	case INIT_BYTE:
	INFO("UART: Connected\n");
	/* Nothing to do */
	continue;

	case GET_CMD_COMMAND:
	ret = get_cmd_command();
	break;

	case GET_VER_COMMAND:
	ret = get_version_command();
	break;

	case GET_ID_COMMAND:
	ret = get_id_command();
	break;

	case PHASE_COMMAND:
	ret = uart_send_phase((uint32_t)buffer);
	if ((ret == 0) && (handle.phase == PHASE_RESET)) {
	start_done = true;
	INFO("UART: Reset\n");
	}
	break;

	case DOWNLOAD_COMMAND:
	ret = uart_download_part();
	break;

	case START_COMMAND:
	ret = uart_start_cmd(buffer);
	if ((ret == 0) && (handle.phase == id)) {
	INFO("UART: Start phase %u\n", handle.phase);
	start_done = true;
	}
	break;

	default:
	WARN("UART: Unknown command\n");
	ret = -EINVAL;
	break;
	}

	if (ret == 0) {
	ret = uart_send_result(ACK_BYTE);
	} else {
	ret = uart_send_result(NACK_BYTE);
	}
	if (ret != 0) {
	return ret;
	}
	}

	stm32_uart_flush(&handle.uart);

	return 0;
	}

	/* Init UART: 115200, 8bit 1stop parity even and enable FIFO mode */
	const struct stm32_uart_init_s init = {
	.baud_rate = STM32MP_UART_BAUDRATE,
	.word_length = STM32_UART_WORDLENGTH_9B,
	.stop_bits = STM32_UART_STOPBITS_1,
	.parity = STM32_UART_PARITY_EVEN,
	.hw_flow_control = STM32_UART_HWCONTROL_NONE,
	.mode = STM32_UART_MODE_TX_RX,
	.fifo_mode = STM32_UART_FIFOMODE_EN,
	};

	int stm32cubeprog_uart_load(uintptr_t instance, uintptr_t base, size_t len)
	{
	int ret;

	if (stm32_uart_init(&handle.uart, instance, &init) != 0) {
	return -EIO;
	}

	/*
	* The following NACK_BYTE is written because STM32CubeProgrammer has
	* already sent its command before TF-A has reached this point, and
	* because FIFO was not configured by BootROM.
	* The byte in the UART_RX register is then the checksum and not the
	* command. NACK_BYTE has to be written, so that the programmer will
	* re-send the good command.
	*/
	ret = uart_send_result(NACK_BYTE);
	if (ret != 0) {
	return ret;
	}

	return uart_read(PHASE_SSBL, base, len);
	}