案例题目： HZ49A65卡LOGO
关联产品： HZ49A65
机芯方案： Hi3751v5510
故障现象： 卡在开机界面
故障原因分析： 卡在开机界面如果检测LDO，DC-DC电压输出均正常时，升级引导和主城还未排除故障时，可以引起此故障的元件常见的有CPU，EMMC DDR损坏。
检修过程： 本故障机机的最后结尾的打印信息如下，仅供维修参考：
4082] init: couldn’t write 1606 to /sys/fs/cgroup/stune/foreground/tasks: No such file or directory
[ 2.072091] init: couldn’t write 1612 to /sys/fs/cgroup/stune/foreground/tasks: No such file or directory
[ 2.086197] init: couldn’t write 1610 to /dev/cpuset/system-background/tasks: No such file or directory
[ 3.748736] init: Service toltech does not have a SELinux domain defined.
[ 5.721492] pgd = ffffffc073728000
[ 5.724883] [0000009c] *pgd=0000000000000000, *pud=0000000000000000
[ 8.811371] init: couldn’t write 1991 to /sys/fs/cgroup/stune/foreground/tasks: No such file or directory
[ 8.814189] init: couldn’t write 1992 to /dev/stune/foreground/tasks: No such file or directory
[ 8.839500] init: cannot find ‘/system/bin/teecd’ (No such file or directory), disabling ‘teecd’
[ 8.908066] init: cannot setexeccon(‘u:r:logwrapper:s0’): Invalid argument
<IAMREADY>
[ 8.977821] init: cannot setexeccon(‘u:r:logwrapper:s0’): Invalid argument
[ 9.441470] Unable to handle kernel paging request at virtual address
本机为DDR损坏 DDR型号：K4A8G165WB-BCRC 位号（N60）,更换DDR后故障排除。
故障板号： RSAG7.820.7941
故障元件： K4A8G165WB-BCRC