ARM Linux BOOTLOADER全程详解（6） default, command, Linux

yuyang911220

static void setup_memory_tags(void)
{
int i; for(i = 0; i < NUM_MEM_AREAS; i++) {
if(memory_map[i].used) {
params->hdr.tag = ATAG_MEM;
params->hdr.size = tag_size(tag_mem32);
params->u.mem.start = memory_map[i].start;
params->u.mem.size = memory_map[i].len;
params = tag_next(params);
}
}
}

static void setup_commandline_tag(char *commandline)
{
int i = 0;
/* skip non-existent command lines so the kernel will still
* use its default command line.
*/
params->hdr.tag = ATAG_CMDLINE;
params->hdr.size = 8;
//console=ttyS0,115200n8
strcpy(params->u.cmdline.cmdline, p);
params = tag_next(params);
}

static void setup_initrd2_tag(void)
{
/* an ATAG_INITRD node tells the kernel where the compressed
* ramdisk can be found. ATAG_RDIMG is a better name, actually.
*/
params->hdr.tag = ATAG_INITRD2;
params->hdr.size = tag_size(tag_initrd);
params->u.initrd.start = RAM_COMPRESSED_RAMDISK_BASE;
params->u.initrd.size = 2047;//k byte
params = tag_next(params);
}

static void setup_ramdisk_tag(void)
{
/* an ATAG_RAMDISK node tells the kernel how large the
* decompressed ramdisk will become.
*/
params->hdr.tag = ATAG_RAMDISK;
params->hdr.size = tag_size(tag_ramdisk);
params->u.ramdisk.start = RAM_DECOMPRESSED_RAMDISK_BASE;
params->u.ramdisk.size = 7.8*1024; //k byte
params->u.ramdisk.flags = 1; // automatically load ramdisk
params = tag_next(params);
}

static void setup_end_tag(void)
{
params->hdr.tag = ATAG_NONE;
params->hdr.size = 0;
} void Uart_Init(int pclk,int baud)//串口是很重要的
{
int i;
if(pclk == 0)
pclk = PCLK;
rUFCON0 = 0x0; //UART channel 0 FIFO control register, FIFO disable
rUMCON0 = 0x0; //UART chaneel 0 MODEM control register, AFC disable
//UART0
rULCON0 = 0x3; //Line control register : Normal,No parity,1 stop,8 bits
下面这段samsung好象写的不太对,但是我按照Normal,No parity,1 stop,8 bits算出来的确是0x245
// [10] [9] [8] [7] [6] [5] [4] [3:2] [1:0]
// Clock Sel, Tx Int, Rx Int, Rx Time Out, Rx err, Loop-back, Send break, Transmit Mode, Receive Mode
// 0 1 0 , 0 1 0 0 , 01 01
// PCLK Level Pulse Disable Generate Normal Normal Interrupt or Polling
rUCON0 = 0x245; // Control register
rUBRDIV0=( (int)(PCLK/16./ baud) -1 ); //Baud rate divisior register 0
delay(10);
}
经过以上的折腾,接下来就是kernel的活了.能不能启动kernel,得看你编译kernel的水平了. 这个BOOTLOADER不象blob那样需要交互信息,使用虚拟地址,总的来说非常简洁明了.