请问为什么用uboot的 tftp命令下载kernel，启动后无打印信息？应该如何解决？

本帖最后由 一只耳朵怪 于 2018-6-20 16:03 编辑

kernel: linux-3.14.43
platform:AM437X
问题：用uboot的 tftp命令下载kernel，启动后无打印信息
tftp操作步骤：
step1: tftp 0x82000000 uImage
step2: tftp 0x83000000 am437x-gp-easyevm.dtb
step3: bootm 0x82000000 - 0x83000000
打印信息如下
U-Boot# U-Boot# U-Boot# U-Boot# tftp 0x82000000 uImagelink up on port 0, speed 1000, full duplexUsing cpsw deviceTFTP from server 192.168.65.106; our IP address is 192.168.65.249Filename 'uImage'.Load address: 0x82000000Loading: #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #################################################################         #####################################################         178.7 KiB/sdoneBytes transferred = 4593440 (461720 hex)U-Boot# tftp 0x83000000 am437x-gp-easyevm.dtblink up on port 0, speed 1000, full duplexUsing cpsw deviceTFTP from server 192.168.65.106; our IP address is 192.168.65.249Filename 'am437x-gp-easyevm.dtb'.Load address: 0x83000000Loading: ##########         196.3 KiB/sdoneBytes transferred = 50739 (c633 hex)U-Boot# bootm 0x82000000 - 0x83000000## Booting kernel from Legacy Image at 82000000 ...   Image Name:   Linux-3.14.43   Image Type:   ARM Linux Kernel Image (uncompressed)   Data Size:    4593376 Bytes = 4.4 MiB   Load Address: 80008000   Entry Point:  80008000   Verifying Checksum ... OK## Flattened Device Tree blob at 83000000   Booting using the fdt blob at 0x83000000   Loading Kernel Image ... OK   Loading Device Tree to 8fff0000, end 8ffff632 ... OKStarting kernel ... _____                    _____           _         _   |  _  |___ ___ ___ ___   |  _  |___ ___  |_|___ ___| |_ |     |  _| .'| . | . |  |   __|  _| . | | | -_|  _|  _||__|__|_| |__,|_  |___|  |__|  |_| |___|_| |___|___|_|                |___|                    |___|            Arago Project http://arago-project.org am437x-evm /dev/ttyO0Arago 2015.05 am437x-evm /dev/ttyO0am437x-evm login: rootroot@am437x-evm:~# 而直接从nand启动就有kernel的打印信息
U-Boot SPL 2014.07-00115-g6c69db3 (Jan 30 2016 - 17:32:22)
Could not probe the EEPROM at 0x50
Could not get board ID.
SPL: Please implement spl_start_uboot() for your board
SPL: Direct Linux boot not active!


U-Boot 2014.07-00115-g6c69db3 (Jan 30 2016 - 17:32:22)I2C:   readyDRAM:  512 MiBNAND:  512 MiBMMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1reading uboot.envCould not probe the EEPROM at 0x50Could not get board ID.Net:   cpsw, u***_etherHit any key to stop autoboot:  0switch to partitions #0, OKmmc0 is current deviceSD/MMC found on device 0reading uEnv.txt** Unable to read file uEnv.txt **4576224 bytes read in 212 ms (20.6 MiB/s)50683 bytes read in 9 ms (5.4 MiB/s)Booting from mmc0 ...Kernel image @ 0x82000000 [ 0x000000 - 0x45d3e0 ]## Flattened Device Tree blob at 88000000   Booting using the fdt blob at 0x88000000   Loading Device Tree to 8fff0000, end 8ffff5fa ... OKStarting kernel ...[    0.000000] Booting Linux on physical CPU 0x0[    0.000000] Linux version 3.14.43 (zxp@zxp) (gcc version 4.7.3 20130226 (prerelease) (crosstool-NG linaro-1.13.1-4.7-2013.03-20130313 - Linaro GCC 2013.03) ) #1 Fri Sep 9 16:13:52 CST 2016[    0.000000] CPU: ARMv7 Processor [412fc09a] revision 10 (ARMv7), cr=10c5387d[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache[    0.000000] Machine model: TI AM437x GP EVM[    0.000000] cma: CMA: reserved 24 MiB at 9e400000[    0.000000] Memory policy: Data cache writeback[    0.000000] CPU: All CPU(s) started in SVC mode.[    0.000000] AM437x ES1.2 (sgx neon )[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 129536[    0.000000] Kernel command line: console=ttyO0,115200n8 root=/dev/mmcblk0p2 rw rootfstype=ext4 rootwait[    0.000000] PID hash table entries: 2048 (order: 1, 8192 bytes)[    0.000000] Dentry cache hash table entries: 65536 (order: 6, 262144 bytes)[    0.000000] Inode-cache hash table entries: 32768 (order: 5, 131072 bytes)[    0.000000] Memory: 483656K/522240K available (6215K kernel code, 312K rwdata, 2212K rodata, 269K init, 233K bss, 38584K reserved, 0K highmem)[    0.000000] Virtual kernel memory layout:[    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)[    0.000000]     fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)[    0.000000]     vmalloc : 0xe0800000 - 0xff000000   ( 488 MB)[    0.000000]     lowmem  : 0xc0000000 - 0xe0000000   ( 512 MB)[    0.000000]     pkmap   : 0xbfe00000 - 0xc0000000   (   2 MB)[    0.000000]     modules : 0xbf000000 - 0xbfe00000   (  14 MB)[    0.000000]       .text : 0xc0008000 - 0xc08430c4   (8429 kB)[    0.000000]       .init : 0xc0844000 - 0xc08874cc   ( 270 kB)[    0.000000]       .data : 0xc0888000 - 0xc08d6200   ( 313 kB)[    0.000000]        .bss : 0xc08d6200 - 0xc0910890   ( 234 kB)[    0.000000] NR_IRQS:16 nr_irqs:16 16[    0.000000] GIC CPU mask not found - kernel will fail to boot.[    0.000000] GIC CPU mask not found - kernel will fail to boot.[    0.000000] OMAP clockevent source: timer2