這週翻了翻u-boot-xilinx的原始碼，結合著網上看的對cortexa8、a9的u-boot的原始碼分析，再結合自己在xilinx上下的u-boot原始碼，試著對u-boot的啟動流程進行一下分析，也給自己理一下思路。
u-boot原始碼的目錄結構：
第一階段：
（1）start.s(arch/arm/cpu/armv7/start.s)
在flash中執行的引導**,也就是bootloader中的stage1,負責初始化硬體環境，把u-boot從flash載入到ram中去，對cpu的乙個初始化，然後跳到board/xilinx/zynq/board.c中去執行。
第二階段：
（2）board.c(board/xilinx/zynq/board.c)
選擇板卡晶元的型號，啟動fpga，選擇啟動方式（qspi、sd、jtag、nand、nor）、讀取rom、ram。
（3）cmd/bootm.c和bootmenu.c
（4）然後在include/config/zynq_common.h中定義了z7系列的一些硬體引數配置，比較重要的乙個預設啟動環境配置：
/* default environment */
#ifndef config_extra_env_settings
#define config_extra_env_settings \
"ethaddr=00:0a:35:00:01:22\0" \
"kernel_image=uimage\0" \
"kernel_load_address=0x2080000\0" \
"ramdisk_image=uramdisk.image.gz\0" \
"ramdisk_load_address=0x4000000\0" \
"devicetree_image=devicetree.dtb\0" \
"devicetree_load_address=0x2000000\0" \
"bitstream_image=system.bit.bin\0" \
"boot_image=boot.bin\0" \
"loadbit_addr=0x100000\0" \
"loadbootenv_addr=0x2000000\0" \
"kernel_size=0x500000\0" \
"devicetree_size=0x20000\0" \
"ramdisk_size=0x5e0000\0" \
"boot_size=0xf00000\0" \
"fdt_high=0x20000000\0" \
"initrd_high=0x20000000\0" \
"bootenv=uenv.txt\0" \
"loadbootenv=load mmc 0 $ $\0" \
"importbootenv=echo importing environment from sd ...; " \
"env import -t $ $filesize\0" \
"sd_uenvtxt_existence_test=test -e mmc 0 /uenv.txt\0" \
"preboot=if test $modeboot = sdboot && env run sd_uenvtxt_existence_test; " \
"then if env run loadbootenv; " \
"then env run importbootenv; " \
"fi; " \
"fi; \0" \
"mmc_loadbit=echo loading bitstream from sd/mmc/emmc to ram.. && " \
"mmcinfo && " \
"load mmc 0 $ $ && " \
"fpga load 0 $ $\0" \
"norboot=echo copying linux from nor flash to ram... && " \
"cp.b 0xe2100000 $ $ && " \
"cp.b 0xe2600000 $ $ && " \
"echo copying ramdisk... && " \
"cp.b 0xe2620000 $ $ && " \
"bootm $ $ $\0" \
"qspiboot=echo copying linux from qspi flash to ram... && " \
"sf probe 0 0 0 && " \
"sf read $ 0x100000 $ && " \
"sf read $ 0x600000 $ && " \
"echo copying ramdisk... && " \
"sf read $ 0x620000 $ && " \
"bootm $ $ $\0" \
"uenvboot=" \
"if run loadbootenv; then " \
"echo loaded environment from $; " \
"run importbootenv; " \
"fi; " \
"if test -n $uenvcmd; then " \
"echo running uenvcmd ...; " \
"run uenvcmd; " \
"fi\0" \
"sdboot=if mmcinfo; then " \
"run uenvboot; " \
"echo copying linux from sd to ram... && " \
"load mmc 0 $ $ && " \
"load mmc 0 $ $ && " \
"load mmc 0 $ $ && " \
"bootm $ $ $; " \
"fi\0" \
"usbboot=if usb start; then " \
"run uenvboot; " \
"echo copying linux from usb to ram... && " \
"load usb 0 $ $ && " \
"load usb 0 $ $ && " \
"load usb 0 $ $ && " \
"bootm $ $ $; " \
"fi\0" \
"nandboot=echo copying linux from nand flash to ram... && " \
"nand read $ 0x100000 $ && " \
"nand read $ 0x600000 $ && " \
"echo copying ramdisk... && " \
"nand read $ 0x620000 $ && " \
"bootm $ $ $\0" \
"jtagboot=echo tftping linux to ram... && " \
"tftpboot $ $ && " \
"tftpboot $ $ && " \
"tftpboot $ $ && " \
"bootm $ $ $\0" \
"rsa_norboot=echo copying image from nor flash to ram... && " \
"cp.b 0xe2100000 0x100000 $ && " \
"zynqrsa 0x100000 && " \
"bootm $ $ $\0" \
"rsa_nandboot=echo copying image from nand flash to ram... && " \
"nand read 0x100000 0x0 $ && " \
"zynqrsa 0x100000 && " \
"bootm $ $ $\0" \
"rsa_qspiboot=echo copying image from qspi flash to ram... && " \
"sf probe 0 0 0 && " \
"sf read 0x100000 0x0 $ && " \
"zynqrsa 0x100000 && " \
"bootm $ $ $\0" \
"rsa_sdboot=echo copying image from sd to ram... && " \
"load mmc 0 0x100000 $ && " \
"zynqrsa 0x100000 && " \
"bootm $ $ $\0" \
"rsa_jtagboot=echo tftping image to ram... && " \
"tftpboot 0x100000 $ && " \
"zynqrsa 0x100000 && " \
"bootm $ $ $\0" \
dfu_alt_info \
bootenv
#endif
u-boot 給kernel 傳引數和kernel 讀取引數，.u-boot 給kernel 傳ram 引數bootm.c 檔案中， bootm 命令對應的 do_bootm 函式，當分析 uimage 中資訊發現 os 是 linux 時 ， 呼叫 ./arch/arc/include/lib/bootm.c 檔案中的 do_bootm_linux 函式來啟動 linux kernel 。
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