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.c
109 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_INIT
118 spl_board_init(); // 启动了 I2C， 并使用I2C控制 PMIC
119 #endif
120
121 boot_device = omap_boot_device(); // 选择启动设备，是nand还是mmc
122
123 switch (boot_device) {
124 #ifdef CONFIG_SPL_MMC_SUPPORT
125 case BOOT_DEVICE_MMC1:
126 case BOOT_DEVICE_MMC2:
127 printk("Booting from MMC...\n");
128 spl_mmc_load_image();
129 break;
130 #endif
131 #ifdef CONFIG_SPL_NAND_SUPPORT
132 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 }