4.720 0.004: Starting kernel ...
4.720 0.000:
5.288 0.568: Uncompressing Linux... done, booting the kernel.
10.584 5.296: [ 0.000000] Linux version 3.2.0 (pc335@pc335) (gcc version 4.5.3 20110311 (prerelease) (GCC) ) #450 Tue Aug 18 14:34:00 CST 2015
10.592 0.008: [ 0.000000] CPU: ARMv7 Processor [413fc082] revision 2 (ARMv7), cr=10c53c7d
10.600 0.007: [ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
10.604 0.004: [ 0.000000] Machine: am335xevm
10.608 0.004: [ 0.000000] Memory policy: ECC disabled, Data cache writeback
以上是SD启动的打印出来的部分信息
红色字体部分，第一句打印到下一句打印，花费了5.296s，这部分启动为什么这么费时？如何优化？求解
