/** USB DFU bootloader
 *  @file
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @copyright SPDX-License-Identifier: GPL-3.0-or-later
 *  @date 2017-2019
 */
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdbool.h> // boolean types

/* STM32 (including CM3) libraries */
#include <libopencm3/cm3/scb.h> // vector table definition
#include <libopencm3/stm32/rcc.h> // clock utilities
#include <libopencm3/stm32/gpio.h> // GPIO utilities

/* own libraries */
#include "global.h" // board definitions
#include "usb_dfu.h" // USB DFU utilities

/** bootloader entry point */
void main(void);
void main(void)
{
	// check of DFU mode is forced
	bool dfu_force = false; // to remember if DFU mode is forced
	// check if DFU magic DFU! has been written to RAM (e.g. by application to indicate we want to start the DFU bootloader)
	if ('D' == __dfu_magic[0] && 'F' == __dfu_magic[1] && 'U' == __dfu_magic[2] && '!' == __dfu_magic[3]) { // verify if the DFU magic is set
		dfu_force = true;
		// clear DFU magic
		__dfu_magic[0] = 0;
		__dfu_magic[1] = 0;
		__dfu_magic[2] = 0;
		__dfu_magic[3] = 0;
	} else if (0 == (RCC_CSR & 0xfc000000)) { // no reset flag present -> this was a soft reset using scb_reset_core() after clearing the flags using RCC_CSR_RMVF, this was the legacy way to start the DFU mode
		dfu_force = true;
	} else { // check if the force DFU mode input is set
		// disable SWJ pin to use as GPIO
#if (defined(DFU_FORCE_PIN) && defined(DFU_FORCE_VALUE))
#if ((GPIO(B) == GPIO_PORT(DFU_FORCE_PIN)) && (GPIO(4) == GPIO_PIN(DFU_FORCE_PIN)))
		// JNTRST pin is used as DFU pin
		rcc_periph_clock_enable(RCC_AFIO); // enable clock for alternate function domain
		gpio_primary_remap(AFIO_MAPR_SWJ_CFG_FULL_SWJ_NO_JNTRST, 0); // keep SWJ enable bit don't use JNTRST
#elif ((GPIO(B) == GPIO_PORT(DFU_FORCE_PIN)) && (GPIO(3) == GPIO_PIN(DFU_FORCE_PIN))) || ((GPIO(A) == GPIO_PORT(DFU_FORCE_PIN)) && (GPIO(15) == GPIO_PIN(DFU_FORCE_PIN)))
		// JTAG but not SWD pin used as DFU pin
		rcc_periph_clock_enable(RCC_AFIO); // enable clock for alternate function domain
		gpio_primary_remap(AFIO_MAPR_SWJ_CFG_JTAG_OFF_SW_ON, 0); // disable JTAG but keep SWD
#elif ((GPIO(A) == GPIO_PORT(DFU_FORCE_PIN)) && (GPIO(14) == GPIO_PIN(DFU_FORCE_PIN))) || ((GPIO(A) == GPIO_PORT(DFU_FORCE_PIN)) && (GPIO(13) == GPIO_PIN(DFU_FORCE_PIN)))
		// JTAG and SWD pin used as DFU pin
		rcc_periph_clock_enable(RCC_AFIO); // enable clock for alternate function domain
		gpio_primary_remap(AFIO_MAPR_SWJ_CFG_JTAG_OFF_SW_OFF, 0); // disable JTAG and SWD
#endif // DFU_FORCE_PIN
		rcc_periph_clock_enable(GPIO_RCC(DFU_FORCE_PIN)); // enable clock for GPIO domain
		gpio_set_mode(GPIO_PORT(DFU_FORCE_PIN), GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, GPIO_PIN(DFU_FORCE_PIN)); // set GPIO to input
		// pull on the opposite of the expected value
#if (DFU_FORCE_VALUE == 1)
		gpio_clear(GPIO_PORT(DFU_FORCE_PIN), GPIO_PIN(DFU_FORCE_PIN)); // pull down to be able to detect when tied to high
		if (gpio_get(GPIO_PORT(DFU_FORCE_PIN), GPIO_PIN(DFU_FORCE_PIN))) { // check if output is set to the value to force DFU mode
#else
		gpio_set(GPIO_PORT(DFU_FORCE_PIN), GPIO_PIN(DFU_FORCE_PIN)); // pull up to be able to detect when tied to low
		if (0 == gpio_get(GPIO_PORT(DFU_FORCE_PIN), GPIO_PIN(DFU_FORCE_PIN))) { // check if output is set to the value to force DFU mode
#endif // DFU_FORCE_VALUE
			dfu_force = true; // DFU mode forced
		}
#endif // defined(DFU_FORCE_PIN)
	}

	// start application if valid
	/* the application starts with the vector table
	 * the first entry in the vector table is the initial stack pointer (SP) address
	 * the stack will be placed in RAM
	 * on STM32F1xx SRAM begins at 0x2000 0000, and on STM32F103xx there is up to 96 KB of RAM (0x18000).
	 * since the stack grown "downwards" it should start at the end of the RAM: max 0x2001 8000
	 * if the SP is not in this range (e.g. flash has been erased) there is no valid application
	 * the second entry in the vector table is the reset address, corresponding to the application start
	 */
	volatile uint32_t* application = (uint32_t*)&__application_beginning; // get the value of the application address symbol (use a register instead on the stack since the stack pointer will be changed)
	if (!dfu_force && (((*application) & 0xFFFE0000) == 0x20000000)) { // application at address seems valid
		SCB_VTOR = (volatile uint32_t)(application); // set vector table to application vector table (store at the beginning of the application)
		__asm__ volatile ("MSR msp,%0" : :"r"(*application)); // set stack pointer to address provided in the beginning of the application (loaded into a register first)
		(*(void(**)(void))((uint32_t)application + 4))(); // start application (by jumping to the reset function which address is stored as second entry of the vector table)
	}

	rcc_clock_setup_in_hse_8mhz_out_72mhz(); // start main clock
	board_setup(); // setup board to control LED
	led_on(); // indicate bootloader started
#if defined(BUSVOODOO)
	led_toggle(); // switch from blue to red LED
#endif
	usb_dfu_setup(); // setup USB DFU for firmware upload
	usb_dfu_start(); // run DFU mode
}