Hi,
... fw_setenv state=2 dd if=... of=/dev/mmcblk0... fw_setenv state=1 ... reboot
Not sure what final "OS" environment you're running, but I would think that "reboot" would sync for you ?
I'm using OpenWRT and reboot links to the busybox implementation. This implemenetation calls sync when I traced it correctly.
According to "man 2 sync":
<quote> DESCRIPTION sync() causes all buffered modifications to file metadata and data to be written to the underlying file systems. </quote>
When I use fw_setenv with /dev/mmcblk0, that means with a block device directly, then I have a problem matching the "filesystem layer" of the description above with the "block layer" which I am using.
Futhermore another quote from the very same man page: <quote> BUGS ...sync() schedules the writes, but may return before the actual writing is done. However, since version 1.3.20 Linux does actually wait. (This still does not guarantee data integrity: modern disks have large caches.) </quote>
So it seems to me, that calling "sync" doesn't do the job.
When looking at "man 2 fsync" I read <quote> ... This includes writing through or flushing a disk cache if present. The call blocks until the device reports that the transfer has completed.... </quote>
This looks much better.
However, I did not trace the call chain in linux kernel down to the block layer yet. Maybe I should.
BR, Michael