On 2008-07-29 12:53 +0800, alex z wrote:
>    Hi All,
>
>    Our nand flash driver is really low, so it takes 4 minutes to mount after
>    not clear umount.
>    mini-UPS is impossible, my system is a handheld product. :)

Some battery-monitoring to make sure that a clean shutdown occurs when
the battery is low, but before the CPU/flash actually starts
operating? Is the problem one of coming back from sleep perhaps, when
the battery is actually too flat to allow that?

>    Is it possible that don't call yaffs_ScanBackwards after not clear umount?
>    It really kills time.

No, that bit is fundamental.

>    Can I use this solution to reduce the mounting time (after normal umount
>    or not clear umount):
>    1) assume the size of yaffs2 partition is 3G, it's called mypartition.
>    2) create a file which is called myfile and its size is 2.9G into
>    mypartition
>    3) after mount mypartition, then mount myfile as vfat filesystem.
>    4) read and write files from/to vfat filesystem.
>
>    Any comment?

As someone explained this is not how flash filesytsenms work.
Can you split your filesystem up into smaller chunks? so the system
mounts first, then data is mounted (so the user gets some feedback?)

Also you should work on optimising your nand driver. As Charles says
4mins is pretty slow - what is the CPU/speed?

and how is it interfaced to
the flash?

You could also up the chunk size from 2K to 4K. If you have
a small number of large files then bigger chunks is a good tradeoff.