我在调试AM3352的板子，使用的是linux3.2内核，使用外部RTC，pcf85063，发现系统硬件时间不能保存。
出现[ 1.948990] pcf85063 3-0051: pcf85063_get_datetime: read error错误，
，请问大概什么原因。
[PENMOUNT] Loading serio-penmount V1.17.3
[ 1.923142] input: PenMountTouch as /devices/virtual/input/input0
[ 1.929879] [PENMOUNT] Registering input device for PenMountTouch!
[ 1.936522] usbcore: registered new interface driver USB-PenMount
[ 1.942958] pcf85063 3-0051: chip found, driver version 1.0
[ 1.948990] pcf85063 3-0051: pcf85063_get_datetime: read error
[ 1.955381] pcf85063 3-0051: rtc core: registered pcf85063 as rtc0
[ 1.961991] i2c /dev entries driver
[ 1.966262] Linux video capture interface: v2.00
[ 1.971360] usbcore: registered new interface driver uvcvideo
[ 1.977364] USB Video Class driver (1.1.1)
