请教各位大佬，D1的start.s __start部分是参考哪里怎么实现的？ 还有dram.c又是从那里得到的这些数据，最后的mksunxi 也是搞不懂依据在哪

[baiwen]

最近在使用D1s录制RISC-V体系架构与C编程的课程，参考xboot作者的裸机实验(一直联系不到作者本人)，目前可以直接烧录在DongshanPI-D1s spinor上运行，但是有几个问题 不明所以，不知道到底是怎么得来的，有懂的大佬能帮忙解析一下么？

https://github.com/DongshanPI/DongshanPI-D1s_BareMetal/tree/master/source/start.S

https://github.com/DongshanPI/DongshanPI-D1s_BareMetal/tree/master/source/sys-dram.c

https://github.com/DongshanPI/DongshanPI-D1s_BareMetal/blob/master/source/tools/mksunxi.c

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>

#if 0
static inline uint32_t __swab32(uint32_t x)
{
	return ( (x<<24) | (x>>24) | \
		((x & (uint32_t)0x0000ff00UL)<<8) | \
		((x & (uint32_t)0x00ff0000UL)>>8) );
}
#define cpu_to_le32(x)	(__swab32((uint32_t)(x)))
#define le32_to_cpu(x)	(__swab32((uint32_t)(x)))
#else
#define cpu_to_le32(x)	(x)
#define le32_to_cpu(x)	(x)
#endif

struct boot_head_t {
	uint32_t instruction;
	uint8_t magic[8];
	uint32_t checksum;
	uint32_t length;
	uint8_t spl_signature[4];
	uint32_t fel_script_address;
	uint32_t fel_uenv_length;
	uint32_t dt_name_offset;
	uint32_t reserved1;
	uint32_t boot_media;
	uint32_t string_pool[13];
};

int main (int argc, char *argv[])
{
	struct boot_head_t * h;
	FILE * fp;
	char * buffer;
	int buflen, filelen;
	uint32_t * p;
	uint32_t sum;
	int i, l, loop;
	
	if(argc != 2)
	{
		printf("Usage: mksunxi <bootloader>\n");
		return -1;
	}

	fp = fopen(argv[1], "r+b");
	if(fp == NULL)
	{
		printf("Open bootloader error\n");
		return -1;
	}
	fseek(fp, 0L, SEEK_END);
	filelen = ftell(fp);
	fseek(fp, 0L, SEEK_SET);
	
	if(filelen <= sizeof(struct boot_head_t))
	{
		fclose(fp);
		printf("The size of bootloader too small\n");
		return -1;
	}

	buflen = (filelen + 0x2000) & ~(0x2000 - 1);
	buffer = malloc(buflen);
	memset(buffer, 0, buflen);
	if(fread(buffer, 1, filelen, fp) != filelen)
	{
		printf("Can't read bootloader\n");
		free(buffer);
		fclose(fp);
		return -1;
	}

	h = (struct boot_head_t *)buffer;
	p = (uint32_t *)h;
	l = le32_to_cpu(h->length);
	h->checksum = cpu_to_le32(0x5F0A6C39);
	loop = l >> 2;
	for(i = 0, sum = 0; i < loop; i++)
		sum += le32_to_cpu(p[i]);
	h->checksum = cpu_to_le32(sum);
	
	fseek(fp, 0L, SEEK_SET);
	if(fwrite(buffer, 1, buflen, fp) != buflen)
	{
		printf("Write bootloader error\n");
		free(buffer);
		fclose(fp);
		return -1;
	}

	fclose(fp);
	printf("The bootloader head has been fixed\n");
	return 0;
}

[YuzukiTsuru]

D1的start.s __start部分是参考哪里怎么实现的？

首先是 eGON.BT0，这个Magic是BROM读取的，所以要在头部插入eGON.BT0

还有dram.c又是从那里得到的这些数据

这是使用mctl_hal.S和自己写的一个小裸机编译出的bin，mctl_hal.S全志的sdk里开源了，这个小裸机源码如下 6ee6e31c-72ef-47f5-b69f-0976197bb46a-d1-ddr.zip

最后的mksunxi 也是搞不懂依据在哪

这个是对齐后重新计算校验码的，然后填充在固定的位置让BROM读取，全志系列的老传统了，你看_start那里的checksum只是一个占位符0x12345678，mksunxi就是会对齐块设备然后计算校验填入然后修改长度

https://github.com/YuzukiHD/TinyKasKit/blob/master/sunxiboot/src/bootpack.cpp