跟踪一下 u-boot 2011.09 MLO在 nandflash 下运行的流程
首先，直接进入 start.S
// arch/arm/cpu/armv7/start.S 36 .globl _start 37 _start: b reset // ... ... 136 reset: 137 bl save_boot_params // ... ... 206 call_board_init_f: 207 ldr sp, =(CONFIG_SYS_INIT_SP_ADDR) 208 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 209 ldr r0,=0x00000000 210 bl board_init_f
SPL 的 board_init_f 在 arch/arm/cpu/armv7/omap-common/spl.c 里面
// arch/arm/cpu/armv7/omap-common/spl.c 57 void board_init_f(ulong dummy) 58 { 59 /* 60 * We call relocate_code() with relocation target same as the 61 * CONFIG_SYS_SPL_TEXT_BASE. This will result in relocation getting 62 * skipped. Instead, only .bss initialization will happen. That's 63 * all we need 64 */ 65 debug(">>board_init_f()\n"); 66 relocate_code(CONFIG_SPL_STACK, &gdata, CONFIG_SPL_TEXT_BASE); // 这里又跳回 start.S 67 } arch/arm/cpu/armv7/start.S 221 .globl relocate_code // 全局函数 222 relocate_code: 223 mov r4, r0 /* save addr_sp */ 224 mov r5, r1 /* save addr of gd */ 225 mov r6, r2 /* save addr of destination */ // ... 上面是将 代码拷贝到 memory （RAM）上的过程 336 _board_init_r_ofs: 337 .word board_init_r - _start // 下面就跳到 SPL 的 board_init_r
SPL 的board_init_r 是在 arch/arm/cpu/armv7/omap-common/spl.c 里面
arch/arm/cpu/armv7/omap-common/spl.c109 void board_init_r(gd_t *id, ulong dummy)110 {111 u32 boot_device;112 debug(">>spl:board_init_r()\n");113 114 timer_init();115 i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);116 117 #ifdef CONFIG_SPL_BOARD_INIT118 spl_board_init(); // 启动了 I2C， 并使用I2C控制 PMIC119 #endif120 121 boot_device = omap_boot_device(); // 选择启动设备，是nand还是mmc122 123 switch (boot_device) {124 #ifdef CONFIG_SPL_MMC_SUPPORT125 case BOOT_DEVICE_MMC1:126 case BOOT_DEVICE_MMC2:127 printk("Booting from MMC...\n");128 spl_mmc_load_image();129 break;130 #endif131 #ifdef CONFIG_SPL_NAND_SUPPORT132 case BOOT_DEVICE_NAND:133 printk("Booting from NAND...\n");134 spl_nand_load_image();135 break; arch/arm/cpu/armv7/omap-common/spl_nand.c 33 void spl_nand_load_image(void) 34 { 35 struct image_header *header; 36 switch (omap_boot_mode()) { 37 case NAND_MODE_HW_ECC: 38 debug("spl: nand - using hw ecc\n"); 39 gpmc_init(); 40 nand_init(); 41 break; 42 default: 43 puts("spl: ERROR: This bootmode is not implemented - hanging"); 44 hang(); 45 } // … 65 nand_spl_load_image(CONFIG_SYS_NAND_U_BOOT_OFFS, 66 CONFIG_SYS_NAND_PAGE_SIZE, (void *)header); 67 spl_parse_image_header(header); // 实现完了 spl 加载到 u-boot.img 68 nand_spl_load_image(CONFIG_SYS_NAND_U_BOOT_OFFS, 69 spl_image.size, (void *)spl_image.load_addr); 70 nand_deselect(); 71 } nand_init( 的实现在 drivers/mtd/nand/nand_spl_simple.c 里面
drivers/mtd/nand/nand_spl_simple.c 224 /* nand_init() - initialize data to make nand usable by SPL */ 225 void nand_init(void) 226 { 227 /* 228 * Init board specific nand support 229 */ 230 mtd.priv = &nand_chip; 231 nand_chip.IO_ADDR_R = nand_chip.IO_ADDR_W = 232 (void __iomem *)CONFIG_SYS_NAND_BASE; 233 nand_chip.options = 0; 234 board_nand_init(&nand_chip); 235 236 if (nand_chip.select_chip) 237 nand_chip.select_chip(&mtd, 0); 238 } board_nand_init 的实现在 drivers/mtd/nand/ti81xx_nand.c
drivers/mtd/nand/ti81xx_nand.c 924 int board_nand_init(struct nand_chip *nand) 925 { 926 /* int32_t gpmc_config = 0; */ 927 cs = 0; 928 929 /* 930 * xloader/Uboot's gpmc configuration would have configured GPMC for 931 * nand type of memory. The following logic scans and latches on to the 932 * first CS with NAND type memory. 933 * TBD: need to make this logic generic to handle multiple CS NAND 934 * devices. 935 */ 936 while (cs < GPMC_MAX_CS) { 937 /* Check if NAND type is set */ 938 if ((readl(&gpmc_cfg->cs[cs].config1) & 0xC00) == 0x800) { 939 /* Found it!! */ 940 #ifdef NAND_DEBUG 941 printf("Searching for NAND device @ GPMC CS:%1d\n", cs); 942 #endif 943 break; 944 } 945 cs++; 946 } 947 if (cs >= GPMC_MAX_CS) { 948 printf("NAND: Unable to find NAND settings in " 949 "GPMC Configuration - quitting\n"); 950 return -ENODEV; 951 } 952 953 nand->IO_ADDR_R = (void __iomem *)&gpmc_cfg->cs[cs].nand_dat; 954 nand->IO_ADDR_W = (void __iomem *)&gpmc_cfg->cs[cs].nand_cmd; 955 956 nand->cmd_ctrl = ti81xx_nand_hwcontrol; 957 nand->options = NAND_NO_PADDING | NAND_CACHEPRG | NAND_NO_AUTOINCR; 958 /* If we are 16 bit dev, our gpmc config tells us that */ 959 if ((readl(&gpmc_cfg->cs[cs].config1) & 0x3000) == 0x1000) { 960 nand->options |= NAND_BUSWIDTH_16; 961 } 962 963 nand->chip_delay = 100; 964 965 /* required in case of BCH */ 966 elm_init(); 967 968 /* BCH info that will be correct for SPL or overridden otherwise. */ 969 nand->priv = &bch_priv; 970 971 #ifndef CONFIG_SPL_BUILD 972 /* For undocumented reasons we need to currently keep our environment 973 * in 1-bit ECC so we configure ourself thusly. */ 974 nand_curr_device = 0; 975 ti81xx_nand_switch_ecc(NAND_ECC_HW, 0); 976 #else 977 /* The NAND chip present requires that we have written data in with 978 * at least 4-bit ECC so we configure outself for that in SPL. 979 */ 980 nand->ecc.mode = NAND_ECC_HW_SYNDROME; 981 /* nand->ecc.layout = &hw_bch8_nand_oob; */ 982 nand->ecc.layout = &nand_ecclayout; 983 nand->ecc.size = CONFIG_SYS_NAND_ECCSIZE; 984 nand->ecc.bytes = CONFIG_SYS_NAND_ECCBYTES; 985 nand->ecc.steps = CONFIG_SYS_NAND_ECCSTEPS; 986 nand->ecc.total = CONFIG_SYS_NAND_ECCTOTAL; 987 nand->ecc.hwctl = ti81xx_enable_ecc_bch; 988 nand->ecc.correct = ti81xx_correct_data_bch; 989 nand->ecc.calculate = ti81xx_calculate_ecc_bch; 990 991 if (nand->options & NAND_BUSWIDTH_16) 992 nand->read_buf = nand_read_buf16; 993 else 994 nand->read_buf = nand_read_buf; 995 nand->dev_ready = ti81xx_spl_dev_ready; 996 997 ti81xx_hwecc_init_bch(nand, NAND_ECC_READ); 998 #endif 999 1000 return 0; 1001 }