uboot> sf probe 2
SF: Got idcode 20 20 15
2048 KiB M25P16 at 0:2 is now current device

uboot> sf read 0x2000000 0x300 0x1000

uboot> md.b 0x2000000
02000000: 4a e1 c0 ff 10 62 0a e1 04 0a 40 e1 c2 ff 10 93    J....b....@.....
02000010: 22 6c 10 93 48 60 c2 6f 10 97 4a e1 e0 ff 20 e1    "l..H`.o..J... .
02000020: fd 01 0a e1 04 20 88 4f 10 93 c6 6c 27 01 30 05    ..... .O...l'.0.
02000030: 10 00 00 00 4a e1 e0 ff 40 e1 fa 03 0a e1 0c 20    ....J...@......

uboot> sf erase 0x30000 0x10000

uboot> sf write 0x20000000 0x0 0x100000

uboot> set sfboot 'sf probe 2; sf read 0x2000000 0x300 0x100000; bootm 0x2000000'
uboot> set bootcmd run sfboot
uboot> save

三、代码分析

490 static int do_spi_flash(cmd_tbl_t *cmdtp,int flag,int argc,491                         char * const argv[])
492 {
493         const char *cmd;
494         int ret;
495 
496         /* need at least two arguments */
497         if (argc < 2)//如果参数小于２测，显示使作帮助
498                 goto usage;
499 
500         cmd = argv[1];
501         --argc;
502         ++argv;
503 
504         if (strcmp(cmd,"probe") == 0) {//执行probe时的分支
505                 ret = do_spi_flash_probe(argc,argv);
506                 goto done;
507         }
508 
509         /* The remaining commands require a selected device */
510         if (!flash) {
511                 puts("No SPI flash selected. Please run `sf probe'n");
512                 return 1;
513         }
514 
515         if (strcmp(cmd,"read") == 0 || strcmp(cmd,"write") == 0 ||　　//read/write的分枝
516             strcmp(cmd,"update") == 0)
517                 ret = do_spi_flash_read_write(argc,argv);
518         else if (strcmp(cmd,"erase") == 0)
519                 ret = do_spi_flash_erase(argc,argv);
520 #ifdef CONFIG_CMD_SF_TEST
521         else if (!strcmp(cmd,"test"))
522                 ret = do_spi_flash_test(argc,argv);
523 #endif
524         else
525                 ret = -1;
526 
527 done:
528         if (ret != -1)
529                 return ret;
530 
531 usage:
532         return CMD_RET_USAGE;}

89 static int do_spi_flash_probe(int argc,char * const argv[])
 90 {
 91         unsigned int bus = CONFIG_SF_DEFAULT_BUS;
 92         unsigned int cs = CONFIG_SF_DEFAULT_CS;
 93         unsigned int speed = CONFIG_SF_DEFAULT_SPEED;
 94         unsigned int mode = CONFIG_SF_DEFAULT_MODE;
 95         char *endp;
 96         struct spi_flash *new;
 97 
 98         if (argc >= 2) {
 99                 cs = simple_strtoul(argv[1],&endp,0);
100                 if (*argv[1] == 0 || (*endp != 0 && *endp != ':'))
101                         return -1;
102                 if (*endp == ':') {
103                         if (endp[1] == 0)
104                                 return -1;
105 
106                         bus = cs;
107                         cs = simple_strtoul(endp + 1,0);
108                         if (*endp != 0)
109                                 return -1;
110                 }
111         }
112 
113         if (argc >= 3) {
114                 speed = simple_strtoul(argv[2],0);
115                 if (*argv[2] == 0 || *endp != 0)
116                         return -1;
117         }
118         if (argc >= 4) {
119                 mode = simple_strtoul(argv[3],16);
120                 if (*argv[3] == 0 || *endp != 0)
121                         return -1;
122         }
123 
124         new = spi_flash_probe(bus,cs,speed,mode);//根据外面传入的but/CS来probe你的spi flash
125         if (!new) {
126                 printf("Failed to initialize SPI flash at %u:%un",bus,cs);
127                 return 1;
128         }
129 
130         if (flash)
131                 spi_flash_free(flash);
132         flash = new;
133 
134         return 0;
135 }