uboot_mt7620对SPI flash操作的分析

http://blog.csdn.net/manfeel/article/details/13093931
接上篇文章，AR9331系统与mt7620系统对flash的划分是不一样的，AR系统划分为Flash（可能是作为NAND来处理），而mt7620（mips）系统则划分的比较明确，用的是SPI_FLASH。

在uboot的启动界面上，可以看到这样一些信息：

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1. Please choose the operation:   
2.    1: Load system code to SDRAM via TFTP.   
3.    2: Load system code then write to Flash via TFTP.   
4.    3: Boot system code via Flash (default).  
5.    4: Entr boot command line interface.  
6.    7: Load Boot Loader code then write to Flash via Serial.   
7.    9: Load Boot Loader code then write to Flash via TFTP.   

于是，

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1. grep 'write to Flash via TFTP' -r .  

打开board.c一看究竟。

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void OperationSelect(void)
{
    printf("\nPlease choose the operation: \n");
    printf("   %d: Load system code then write to Flash via Serial. \n", SEL_LOAD_LINUX_WRITE_FLASH_BY_SERIAL);
    printf("   %d: Load system code to SDRAM via TFTP. \n", SEL_LOAD_LINUX_SDRAM);
    printf("   %d: Load system code then write to Flash via TFTP. \n", SEL_LOAD_LINUX_WRITE_FLASH);
    printf("   %d: Boot system code via Flash (default).\n", SEL_BOOT_FLASH);
#ifdef RALINK_CMDLINE
    printf("   %d: Entr boot command line interface.\n", SEL_ENTER_CLI);
#endif // RALINK_CMDLINE //

#if defined(ASUS_RTN14U)
    printf("   %d: Load Boot Loader code to SDRAM via Serial. \n", SEL_LOAD_BOOT_SDRAM_VIA_SERIAL);
#endif
#ifdef RALINK_UPGRADE_BY_SERIAL
    printf("   %d: Load Boot Loader code then write to Flash via Serial. \n", SEL_LOAD_BOOT_WRITE_FLASH_BY_SERIAL);
#endif // RALINK_UPGRADE_BY_SERIAL //

#if defined(ASUS_RTN14U)
    printf("   %d: Load Boot Loader code to SDRAM via TFTP. \n", SEL_LOAD_BOOT_SDRAM);
#endif
    printf("   %d: Load Boot Loader code then write to Flash via TFTP. \n", SEL_LOAD_BOOT_WRITE_FLASH);
}

调用层次为：【./cpu/ralink_soc/start.S: la t9, board_init_r】→【board_init_r】→【OperationSelect】

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        case '2':
            printf("   \n%d: System Load Linux Kernel then write to Flash via TFTP. \n", SEL_LOAD_LINUX_WRITE_FLASH);
            printf(" Warning!! Erase Linux in Flash then burn new one. Are you sure?(Y/N)\n");
            confirm = getc();
            if (confirm != 'y' && confirm != 'Y') {
                printf(" Operation terminated\n");
                break;
            }
            tftp_config(SEL_LOAD_LINUX_WRITE_FLASH, argv);
            argc= 3;
            setenv("autostart", "no");
            do_tftpb(cmdtp, 0, argc, argv);

#if defined (CFG_ENV_IS_IN_NAND)
            if (1) {
                unsigned int load_address = simple_strtoul(argv[1], NULL, 16);
                ranand_erase_write((u8 *)load_address, CFG_KERN_ADDR-CFG_FLASH_BASE, NetBootFileXferSize);
            }
#elif defined (CFG_ENV_IS_IN_SPI)
            if (1) {
                unsigned int load_address = simple_strtoul(argv[1], NULL, 16);
                raspi_erase_write((u8 *)load_address, CFG_KERN_ADDR-CFG_FLASH_BASE, NetBootFileXferSize);
            }
#else //CFG_ENV_IS_IN_FLASH
#if (defined (ON_BOARD_8M_FLASH_COMPONENT) || defined (ON_BOARD_16M_FLASH_COMPONENT)) && (defined (RT2880_ASIC_BOARD) || defined (RT2880_FPGA_BOARD) || defined (RT3052_MP1))
            //erase linux
            if (NetBootFileXferSize <= (0x400000 - (CFG_BOOTLOADER_SIZE + CFG_CONFIG_SIZE + CFG_FACTORY_SIZE))) {
                e_end = CFG_KERN_ADDR + NetBootFileXferSize;
                if (0 != get_addr_boundary(&e_end))
                    break;
                printf("Erase linux kernel block !!\n");
                printf("From 0x%X To 0x%X\n", CFG_KERN_ADDR, e_end);
                flash_sect_erase(CFG_KERN_ADDR, e_end);
            }
            else if (NetBootFileXferSize <= CFG_KERN_SIZE) {
                e_end = PHYS_FLASH_2 + NetBootFileXferSize - (0x400000 - (CFG_BOOTLOADER_SIZE + CFG_CONFIG_SIZE + CFG_FACTORY_SIZE));
                if (0 != get_addr_boundary(&e_end))
                    break;
                printf("Erase linux kernel block !!\n");
                printf("From 0x%X To 0x%X\n", CFG_KERN_ADDR, CFG_FLASH_BASE+0x3FFFFF);
                flash_sect_erase(CFG_KERN_ADDR, CFG_FLASH_BASE+0x3FFFFF);
                printf("Erase linux file system block !!\n");
                printf("From 0x%X To 0x%X\n", PHYS_FLASH_2, e_end);
                flash_sect_erase(PHYS_FLASH_2, e_end);
            }
#else
            if (NetBootFileXferSize <= (bd->bi_flashsize - (CFG_BOOTLOADER_SIZE + CFG_CONFIG_SIZE + CFG_FACTORY_SIZE))) {
                e_end = CFG_KERN_ADDR + NetBootFileXferSize;
                if (0 != get_addr_boundary(&e_end))
                    break;
                printf("Erase linux kernel block !!\n");
                printf("From 0x%X To 0x%X\n", CFG_KERN_ADDR, e_end);
                flash_sect_erase(CFG_KERN_ADDR, e_end);
            }
#endif
            else {
                printf("***********************************\n");
                printf("The Linux Image size is too big !! \n");
                printf("***********************************\n");
                break;
            }

            //cp.linux
            argc = 4;
            argv[0]= "cp.linux";
            do_mem_cp(cmdtp, 0, argc, argv);
#endif //CFG_ENV_IS_IN_FLASH

#ifdef DUAL_IMAGE_SUPPORT
            /* Don't do anything to the firmware upgraded in Uboot, since it may be used for testing */
            setenv("Image1Stable", "1");
            saveenv();
#endif

            //bootm bc050000
            argc= 2;
            sprintf(addr_str, "0x%X", CFG_KERN_ADDR);
            argv[1] = &addr_str[0];
            do_bootm(cmdtp, 0, argc, argv);
            break;

调用的是 raspi_erase_write 方法来对spi flash进行擦除和写入。