为什么要使能SPL功能呢？

因为根据S3C6410_Internal_ROM_Booting.pdf文档中的启动流程描述，从Nand启动时，系统上电三星固化好的BL0会自动加载Nand中前8K到iROM；
因为u-boot的大小大于8K，BL0无法将所有的u-boot加载到iROM，u-boot为了解决此类设备的问题，引入了SPL。
由SPL (BL1)负责将u-boot (BL2)拷贝到SDRAM，DDR等，然后跳转到BL2中执行。

SPL相关基础

参考之前的学习笔记：

u-boot SPL学习笔记

SPL相关配置

在arch/arm/mach-s3c6410/Kconfig中添加SPPORT_SPL表示支持SPL:

image-20220326225836128 
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#在smdk6410_defconfig中添加

CONFIG_SPL_LOGLEVEL=7

CONFIG_SPL=y
CONFIG_SPL_NAND_BOOT=y
CONFIG_SPL_LDSCRIPT="board/$(BOARDDIR)/u-boot-spl.lds"
CONFIG_SPL_BOARD_INIT=y

#因为IROM 8K，编译时检查SPL文件大小
CONFIG_SPL_MAX_SIZE=8192
CONFIG_SPL_TEXT_BASE=0x0C000000
CONFIG_SPL_STACK=0x0C004080

CONFIG_SYS_SPL_MALLOC_START=0x0C003000
CONFIG_SYS_SPL_MALLOC_SIZE=4096

CONFIG_SPL_NAND_SUPPORT=y


## SPL debug
#CONFIG_SPL_SERIAL_SUPPORT=y

## support printf()
CONFIG_SPL_LIBCOMMON_SUPPORT=y
CONFIG_SPL_LIBGENERIC_SUPPORT=y
CONFIG_SPL_PRINTF=y



#在include/configs/smdk6410.h中定义
/*
* BL1 16K (every 2K of one page, 4page * 2K=8K; 4pages=4*4K=16K)
*/
#define CONFIG_SPL_NAND_RAW_ONLY
#define CONFIG_SYS_NAND_U_BOOT_OFFS       4  /*pages, 4*4096=16K*/
#define CONFIG_SYS_NAND_U_BOOT_DST        CONFIG_SYS_TEXT_BASE
#define CONFIG_SYS_NAND_U_BOOT_SIZE       (512*1024)

#define CONFIG_SYS_MONITOR_LEN  (512*1024)

SPL启动流程

流程

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#根据u-boot-spl.lds链接脚本，入口为_start

_start					# vectors.S
	reset				# arch/cpu/arm1176/start.S
		lowlevel_init	# board/samsung/smdk6410/lowlevel_init.S
			#LED灯，时钟，串口，nand控制器，sdram
		_main			#arch/arm/lib/crt0.S
			#CONFIG_SPL_STACK 堆栈使用SRAM
			#分配16字节对齐的栈空间，返回栈指针
			board_init_f_alloc_reserve()		#common/init/board_init.c
			
			#初始化GD
			board_init_f_init_reserve()			#common/init/board_init.c
			
			#重载board_init_f(),完成板子必要的操作，必须正常返回，不能直接调用board_init_r()
			board_init_f()
			
			#relocate GD结构，如果定义CONFIG_SPL_STACK_R
			#对于一些board_init_r()运行需要更多栈空间的情况，可以定义，然后进行relocate，从而使用SDRAM栈空间
			spl_relocate_stack_gd()
			
			#清除BSS
			
			#调用board_init_r
			mov     r0, r9                  /* gd_t */
			ldr	r1, [r9, #GD_RELOCADDR]		/* dest_addr */
			ldr	pc, =board_init_r
			
			board_init_r()					#common/spl/spl.c
				spl_set_bd()				#common/spl/spl.c
				spl_init()					#common/spl/spl.c
					spl_common_init()	
                    	#启动流程记录，主要用于log
						bootstage_init()	#include/bootstage.h
                        #of_control dts相关初始化(可选，未启用)
                        #dm相关初始化(可选，未启用)
                    
                    #定时器初始化,10ms
                    timer_init()			#arch/arm/mach-s3c6410/timer.c
                    #是否初始化板子其他硬件(可选未启用)，通过定义CONFIG_BOARD_INIT启用;需要自己实现
                   	spl_board_init()
                   	#启动次数计数(未使用)
                    bootcount_inc()
                    
                    #配置启动顺序，这里选择的是:BOOT_DEVICE_NAND
                    board_boot_order()
                    	spl_boot_device()	#board/samsung/smdk6410.c
                    
                    #从nand启动
                    boot_from_devices()		#common/spl/spl.c
                    	#spl_ll_find_loader()从`.u_boot_list`段中查找boot入口, 
                    	spl_ll_find_loader()
                    	
                    	#拷贝BL2到SDRAM
                    	spl_load_image()			#common/spl/spl_nand.c
                    		nand_init()				#board/samsung/smdk6410/smdk6410.c
                    		nand_spl_load_image()	#board/samsung/smdk6410/smdk6410.c
                    		spl_set_header_raw_uboot() #common/spl/spl.c
                    			spl_image->size = CONFIG_SYS_MONITOR_LEN
                    			spl_image->entry_point = CONFIG_SYS_UBOOT_START;
								spl_image->load_addr = CONFIG_SYS_TEXT_BASE;
							
                    	nand_deselect()			#board/samsung/smdk6410.c	
                    
                    #跳转前的准备
                    spl_board_prepare_for_boot()
                    
                    #跳转到u-boot(BL2)
                    jump_to_image_no_args()

gd在哪里定义的

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//arch/arm/include/asm/global_data.h

#ifdef __clang__ //如果使用__clang__编译器

#else //否则

#ifdef CONFIG_ARM64
#define DECLARE_GLOBAL_DATA_PTR		register volatile gd_t *gd asm ("x18")
#else

#define DECLARE_GLOBAL_DATA_PTR		register volatile gd_t *gd asm ("r9")	//32位arm,使用r9来存放gd首地址
#endif

#endif

需要自己实现哪些函数

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/*
* timer_init(): arm/arch/mach-s3c6410/timer.c
*/

int timer_init(void)
{
	S3C64XX_TIMERS *const timers = S3C64XX_GetBase_TIMERS();

	/* use PWM Timer 4 because it has no output */
	/* prescaler for Timer 4 is 16 */
	timers->TCFG0 = 0x0f00;
	if (timer_load_val == 0) {
		/*
		 * for 10 ms clock period @ PCLK with 4 bit divider = 1/2
		 * (default) and prescaler = 16. Should be 10390
		 * @33.25MHz and 15625 @ 50 MHz
		 */
		timer_load_val = get_PCLK() / (2 * 16 * 100);
	}

	/* load value for 10 ms timeout */
	lastdec = timers->TCNTB4 = timer_load_val;
	/* auto load, manual update of Timer 4 */
	timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | TCON_4_UPDATE;
	/* auto load, start Timer 4 */
	timers->TCON = (timers->TCON & ~0x00700000) | TCON_4_AUTO | COUNT_4_ON;
	timestamp = 0;

	return (0);
}

/*
* nand_init(): board/samsung/smdk6410/smdk6410.c
*/
void nand_init(void)
{
	//do nothing, cause has init in lowlevel_init.S
}

/*
* nand_deselect(): board/samsung/smdk6410/smdk6410.c
*/
void nand_deselect(void)
{
}

void  board_init_f(ulong dummy)
{
    
}

nand_spl_load_image()

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//board/samsung/smdk6410/bl1_nand_copy.c

#include <common.h>
#include <nand.h>
#include <asm/arch/hardware.h>
#include <asm/arch/nand-regs.h>
#include <asm/arch/bootnand.h>

#include <asm/io.h>

/*
 * address format
 * 1 0 7       0|7 6          0|    3   0|7    0
 * --------------------------------------------
 * | block(11bit) | page(7bit) | offset(12bit) |
 * --------------------------------------------
 */

static int nandll_read_page(uchar *buf, ulong addr, int large_block)
{
	uchar *pdest_sdram_addr = (uchar *)buf;
	int i;
	int page_size = 512;
	uchar temp = 0;

	if (large_block == 1)
		page_size = 2048;
	if (large_block == 2)
		page_size = 4096;
	if (large_block == 3)
		page_size = 8192;

	NAND_ENABLE_CE();

	NFCMD_REG = NAND_CMD_READ0;

	/* Write Address */

	/*页内地址11bit: 0，读一整页所以从0开始*/
	NFADDR_REG = 0;
	if (large_block)
		NFADDR_REG = 0;

	/*页地址0-bit6, 块地址0：bit7：*/
	NFADDR_REG = (addr)&0xff;

	/*块地址1-8: */
	NFADDR_REG = (addr >> 8) & 0xff;

	/*块地址9-10*/
	NFADDR_REG = (addr >> 16) & 0xff;

	if (large_block)
		NFCMD_REG = NAND_CMD_READSTART;

	NF_TRANSRnB();

	/* for compatibility(2460). u32 cannot be used. by scsuh */
	for (i = 0; i < page_size; i++)
	{
		temp = NFDATA8_REG;
		*pdest_sdram_addr++ = temp;
		/*
		if(i<32 && addr == 4) {
			asm_print_hex(temp);
			asm_puts(" ");
		}
		*/
	}
	NAND_DISABLE_CE();
	return 0;
}


// #define NF8_ReadPage_Adv(a,b,c) (((int(*)(uint32, uint32, uint8*))(*((uint32 *)0x0C004004)))(a,b,c))

/*
 * Read data from NAND.
 */
static int nandll_read_blocks(uint32_t offs, unsigned int size, void *buff, int large_block)
{
	int i;
	uchar *buf = (uchar *)buff;
	uint page_shift = 9;

	if (large_block == 1)
		page_shift = 11;

	/* Read pages */
	if (large_block == 2)
		page_shift = 12;

	if (large_block == 2)
	{ 
		/* Read pages,仅读取BL2 */
		for (i = (0 + offs); i < (offs + (size >> page_shift)); i++, buf += (1 << page_shift))
		{
			nandll_read_page(buf, i, large_block);
		}
		//asm_puts("nandll_read_blocks Done\n");
	}
	else
	{
		for (i = (0 + offs); i < (offs + (size >> page_shift)); i++, buf += (1 << page_shift))
		{
			nandll_read_page(buf, i, large_block);
		}
	}

	return 0;
}

int nand_spl_load_image(uint32_t offs, unsigned int size, void *buf)
{
	int large_block = 0;
	int i;
	vu_char id;

	NAND_ENABLE_CE();
	NFCMD_REG = NAND_CMD_RESET;
	NF_TRANSRnB();

	NFCMD_REG = NAND_CMD_READID;
	NFADDR_REG = 0x00;

	NF_TRANSRnB();

	/* wait for a while */
	for (i = 0; i < 200; i++)
		;

	int factory = NFDATA8_REG;
	id = NFDATA8_REG;

	int cellinfo = NFDATA8_REG;
	int tmp = NFDATA8_REG;

	//int childType=tmp & 0x03; //Page size
	int childType = cellinfo; //Page size

	if (id > 0x80)
	{
		large_block = 1;
	}

	if (id == 0xd5 && childType == 0x94) //K9GAG08U0D
	{
		large_block = 2;
	}
	if (id == 0xd5 && childType == 0x14) //K9GAG08U0M
	{
		large_block = 2;
	}
	if (id == 0xd5 && childType == 0x84) //K9GAG08U0E
	{
		large_block = 3;
	}
	if (id == 0xd7) //K9LBG08U0D
	{
		large_block = 2;
	}
	if (factory == 0x2c && id == 0x48) //MT29F16G08ABACAWP
	{
		large_block = 2;
	}
	if (factory == 0x2c && id == 0x38) //MT29F8G08ABABAWP
	{
		large_block = 2;
		//asm_puts("large_block=2\n");
	}

	nandll_read_blocks(offs, size, buf, large_block);

	NAND_DISABLE_CE();

	return 0;
}

有关于nand flash的地址问题，这里使用的是MT29F8G08ABABAWP，datasheet关于地址的描述如下：

LUN or Die结构图：

LUN or Die结构图

列地址(column addr) –页内地址CA0-CA11 12bit

行地址(row addr)– 页地址PA0-PA6 7bit, 块地址BA7-BA17 11bit

时序图：

Page Read时序图

如何跳转到BL2的

通过jump_to_image_no_args()函数，通过函数指针，转换城汇编就是通过ldr pc, =entry_point ：

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//
__weak void __noreturn jump_to_image_no_args(struct spl_image_info *spl_image)
{
	typedef void __noreturn (*image_entry_noargs_t)(void);

	image_entry_noargs_t image_entry =
		(image_entry_noargs_t)spl_image->entry_point;

	debug("image entry point: 0x%lX\n", spl_image->entry_point);
	//asm_puts("will jump to u-boot...\n");
	image_entry();
}

SPL & u-boot合并成一个文件

因为u-boot烧写到nand flash中，是通过飞凌提供的uboot1.1.6源码编译的sd卡启动版本u-boot；

所以按照sd卡中的u-boot烧写流程，需要将SPL(BL1)和u-boot(BL2)合并成一个文件。

根据三星固化的BL0程序，上电时只读取每个page的前2K，一共读取4page合并成8K，所以BL2的偏移地址为8192 。

合并shell脚本run_combine.sh, 位于u-boot源码的根目录：

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#!/bin/bash

SPL=./build/spl/u-boot-spl.bin
UBOOT=./build/u-boot.bin
TMP_FILL=./build/tmp_ff.bin
COMBINE=./u-boot.bin


#caculate spl file size
SPL_SIZE=`ls -l $SPL | awk '{print $5}' | tr -d '\n'`


BL1_SIZE=8192 #20K
BL1_FILL_SIZE=`expr $BL1_SIZE - $SPL_SIZE`

echo "----spl size=$SPL_SIZE byte, need fill $BL1_FILL_SIZE byte."

echo "----create $TMP_FILL...."
rm -rf $TMP_FILL
tr '\000' '\377' < /dev/zero | dd of=$TMP_FILL bs=1 count=$BL1_FILL_SIZE


echo "----combine spl & u-boot...."
rm -rf $COMBINE
cat $SPL $TMP_FILL $UBOOT > $COMBINE

echo "----Done."

参考

关于Nand Flash行地址和列地址的计算