以uboot2010.06为例解说norflash工作原理
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根据根目录makefile文件得知系统从start.S启动，在start.S里面看到函数跳转到start_armboot 里面调用了flash_init ()初始化，这里我们知道是对flash进行初始化。那么这个函数在哪里呢？ 在board/samsung/smdk2440/flash.c下。于是我们在这个flash.c文件下分析flash
我用的norflash是EN29LV160AB这个型号，和uboot源码里有些出入 所以在分析的过程中我们适当更改部分配置
先从宏定义开始看
#define FLASH_BANK_SIZE PHYS_FLASH_SIZE //从字面分析 应该是定义flashBANK空间 我们的flash是2M的 所有后面的PHYS_FLASH_SIZE = 0x20000000
#define MAIN_SECT_SIZE 0x8000 /* 32 KB */ //定义了主要的sect（扇区）大小，看EN29LV手册 我们总共有35个扇区 31个大小为32K
flash_info_t flash_info[CONFIG_SYS_MAX_FLASH_BANKS];
//其中CONFIG_SYS_MAX_FLASH_BANKS在smdk2410.h里定义#define CONFIG_SYS_MAX_FLASH_SECT (35) /* max number of sectors on one chip */
#define CMD_READ_ARRAY 0x000000F0 //下面几个宏定义在EN29LV里面都有说明 是常用的命令数据
#define CMD_UNLOCK1 0x000000AA
#define CMD_UNLOCK2 0x00000055
#define CMD_ERASE_SETUP 0x00000080
#define CMD_ERASE_CONFIRM 0x00000030
#define CMD_PROGRAM 0x000000A0
#define CMD_UNLOCK_BYPASS 0x00000020
//以下两个宏为EN29LV手册中提到的命令写入的地址一个是0x555 一个是2AA 至于为什么左移一位，是设计时 norflash的地址A0通常接ARM芯片地址的A1为 所以地址左移
#define MEM_FLASH_ADDR1 (*(volatile u16 *)(CONFIG_SYS_FLASH_BASE + (0x00000555 << 1)))
#define MEM_FLASH_ADDR2 (*(volatile u16 *)(CONFIG_SYS_FLASH_BASE + (0x000002AA << 1)))
#define BIT_ERASE_DONE 0x00000080
#define BIT_RDY_MASK 0x00000080
#define BIT_PROGRAM_ERROR 0x00000020
#define BIT_TIMEOUT 0x80000000 /* our flag */
#define READY 1
#define ERR 2
#define TMO 4
//搞清楚了上面的宏定义 再看下面的几个函数就好理解多了。。。。
ulong flash_init (void) //flash初始化函数
{
int i, j;
ulong size = 0;
for (i = 0; i < CONFIG_SYS_MAX_FLASH_BANKS; i++) { //对BANK区初始化 一般只用到BANK0 所以这里只循环一次 这里是通用写法
ulong flashbase = 0;
flash_info[i].flash_id = //根据flash型号 赋予flashid号 我们也可以自定义
#if defined(CONFIG_AMD_LV400)
(AMD_MANUFACT & FLASH_VENDMASK) |
(AMD_ID_LV400B & FLASH_TYPEMASK);
#elif defined(CONFIG_AMD_LV800)
(AMD_MANUFACT & FLASH_VENDMASK) |
(AMD_ID_LV800B & FLASH_TYPEMASK);
#else
#error "Unknown flash configured"
#endif
flash_info[i].size = FLASH_BANK_SIZE; //赋值当前BANK中flash占用大小 这里我们的norflash才2M arm9一个bank有128M 我们只占用了2M
flash_info[i].sector_count = CONFIG_SYS_MAX_FLASH_SECT; //有多少个扇区 前面提到 总共35个
memset (flash_info[i].protect, 0, CONFIG_SYS_MAX_FLASH_SECT); //受保护的扇区
if (i == 0)
flashbase = PHYS_FLASH_1; //flash起始地址 = 0x00000000
else
panic ("configured too many flash banks!n");
for (j = 0; j < flash_info[i].sector_count; j++)
{
if (j <= 3)
{
/* 1st one is 8 KB */
if (j == 0)
{
flash_info[i].start[j] = flashbase + 0; //由EN29LV手册 第一个扇区大小为8K 起始地址为0x00000000
}
/* 2nd and 3rd are both 4 KB */
if ((j == 1) || (j == 2))
{
flash_info[i].start[j] = flashbase + 0x2000 + (j - 1) * 0x1000; //第二个和第三个扇区大小为4K 起始地址紧跟在8K后
}
/* 4th 16 KB */
if (j == 3)
{
flash_info[i].start[j] = flashbase + 0x4000;
}
}
else
{
flash_info[i].start[j] = flashbase + (j - 3) * MAIN_SECT_SIZE; //其余31个扇区皆为32K
}
}
size += flash_info[i].size; //获得整个flash的大小 2M
flash_protect (FLAG_PROTECT_SET,
CONFIG_SYS_FLASH_BASE,
CONFIG_SYS_FLASH_BASE + monitor_flash_len - 1,
&flash_info[0]);
flash_protect (FLAG_PROTECT_SET,
CONFIG_ENV_ADDR,
CONFIG_ENV_ADDR + CONFIG_ENV_SIZE - 1, &flash_info[0]);
return size;
}
int flash_erase (flash_info_t * info, int s_first, int s_last) // flash擦除函数
{
ushort result;
int iflag, cflag, prot, sect;
int rc = ERR_OK;
int chip;
/* first look for protection bits */
if (info->flash_id == FLASH_UNKNOWN)
return ERR_UNKNOWN_FLASH_TYPE;
if ((s_first < 0) || (s_first > s_last)) {
return ERR_INVAL;
}
if ((info->flash_id & FLASH_VENDMASK) !=
(AMD_MANUFACT & FLASH_VENDMASK)) {
return ERR_UNKNOWN_FLASH_VENDOR;
} //以上都是一些验证信息 flash不对 提示错误
prot = 0;
for (sect = s_first; sect <= s_last; ++sect) { //如果有受保护扇区 也擦除不成功
if (info->protect[sect]) {
prot++;
}
}
if (prot)
return ERR_PROTECTED;
/*
* Disable interrupts which might cause a timeout
* here. Remember that our exception vectors are
* at address 0 in the flash, and we don't want a
* (ticker) exception to happen while the flash
* chip is in programming mode.
*/
cflag = icache_status ();
icache_disable ();
iflag = disable_interrupts ();
/* Start erase on unprotected sectors */
for (sect = s_first; sect <= s_last && !ctrlc (); sect++) { //按扇区一个个擦除
printf ("Erasing sector %2d ... ", sect);
/* arm simple, non interrupt dependent timer */
reset_timer_masked ();
if (info->protect[sect] == 0) { /* not protected */
vu_short *addr = (vu_short *) (info->start[sect]); //从第一个扇区开始擦除
MEM_FLASH_ADDR1 = CMD_UNLOCK1; //前面提到过 这些EN29LV手册里都有提示 就是往flash里写命令的格式
MEM_FLASH_ADDR2 = CMD_UNLOCK2;
MEM_FLASH_ADDR1 = CMD_ERASE_SETUP;
MEM_FLASH_ADDR1 = CMD_UNLOCK1;
MEM_FLASH_ADDR2 = CMD_UNLOCK2;
*addr = CMD_ERASE_CONFIRM;
/* wait until flash is ready */
chip = 0;
do {
result = *addr;
/* check timeout */
if (get_timer_masked () >
CONFIG_SYS_FLASH_ERASE_TOUT) {
MEM_FLASH_ADDR1 = CMD_READ_ARRAY;
chip = TMO;
break;
}
if (!chip
&& (result & 0xFFFF) & BIT_ERASE_DONE)
chip = READY;
if (!chip
&& (result & 0xFFFF) & BIT_PROGRAM_ERROR)
chip = ERR;
} while (!chip);
MEM_FLASH_ADDR1 = CMD_READ_ARRAY;
if (chip == ERR) {
rc = ERR_PROG_ERROR;
goto outahere;
}
if (chip == TMO) {
rc = ERR_TIMOUT;
goto outahere;
}
printf ("ok.n");
} else { /* it was protected */
printf ("protected!n");
}
}
if (ctrlc ())
printf ("User Interrupt!n");
outahere:
/* allow flash to settle - wait 10 ms */
udelay_masked (10000);
if (iflag)
enable_interrupts ();
if (cflag)
icache_enable ();
return rc;
}
static int write_hword (flash_info_t * info, ulong dest, ushort data) //向flash里写一个半字 16bit
{
vu_short *addr = (vu_short *) dest; //dest表示flash里的地址
ushort result;
int rc = ERR_OK;
int cflag, iflag;
int chip;
/*
* Check if Flash is (sufficiently) erased
*/
result = *addr;
if ((result & data) != data) //检查flash是否擦除 擦除后就全是FFFF了
return ERR_NOT_ERASED;
/*
* Disable interrupts which might cause a timeout
* here. Remember that our exception vectors are
* at address 0 in the flash, and we don't want a
* (ticker) exception to happen while the flash
* chip is in programming mode.
*/
cflag = icache_status ();
icache_disable ();
iflag = disable_interrupts ();
MEM_FLASH_ADDR1 = CMD_UNLOCK1;
MEM_FLASH_ADDR2 = CMD_UNLOCK2;
MEM_FLASH_ADDR1 = CMD_UNLOCK_BYPASS;
*addr = CMD_PROGRAM; //手册里的写半字命令
*addr = data;
/* arm simple, non interrupt dependent timer */
reset_timer_masked ();
/* wait until flash is ready */
chip = 0;
do {
result = *addr;
/* check timeout */
if (get_timer_masked () > CONFIG_SYS_FLASH_ERASE_TOUT) {
chip = ERR | TMO;
break;
}
if (!chip && ((result & 0x80) == (data & 0x80)))
chip = READY;
if (!chip && ((result & 0xFFFF) & BIT_PROGRAM_ERROR)) {
result = *addr;
if ((result & 0x80) == (data & 0x80))
chip = READY;
else
chip = ERR;
}
} while (!chip);
*addr = CMD_READ_ARRAY;
if (chip == ERR || *addr != data)
rc = ERR_PROG_ERROR;
if (iflag)
enable_interrupts ();
if (cflag)
icache_enable ();
return rc;
}
/*-----------------------------------------------------------------------
* Copy memory to flash.
*/
int write_buff (flash_info_t * info, uchar * src, ulong addr, ulong cnt) //flash写 会调用上面的写hword命令 这个是写一片
{
ulong cp, wp;
int l;
int i, rc;
ushort data;
wp = (addr & ~1); /* get lower word aligned address */
/*
* handle unaligned start bytes
*/
if ((l = addr - wp) != 0) {
data = 0;
for (i = 0, cp = wp; i < l; ++i, ++cp) {
data = (data >> 8) | (*(uchar *) cp << 8);
}
for (; i < 2 && cnt > 0; ++i) {
data = (data >> 8) | (*src++ << 8);
--cnt;
++cp;
}
for (; cnt == 0 && i < 2; ++i, ++cp) {
data = (data >> 8) | (*(uchar *) cp << 8);
}
if ((rc = write_hword (info, wp, data)) != 0) {
return (rc);
}
wp += 2;
}
/*
* handle word aligned part
*/
while (cnt >= 2) {
data = *((vu_short *) src);
if ((rc = write_hword (info, wp, data)) != 0) {
return (rc);
}
src += 2;
wp += 2;
cnt -= 2;
}
if (cnt == 0) {
return ERR_OK;
}
/*
* handle unaligned tail bytes
*/
data = 0;
for (i = 0, cp = wp; i < 2 && cnt > 0; ++i, ++cp) {
data = (data >> 8) | (*src++ << 8);
--cnt;
}
for (; i < 2; ++i, ++cp) {
data = (data >> 8) | (*(uchar *) cp << 8);
}
return write_hword (info, wp, data);
}
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