UBIFS on Atmel Dataflash

Hi guys,

this is my very first try to get UBIFS working. My target is an Atmel AT91RM9200 cpu which has a 8MB Atmel Dataflash AT45DB642x. Pagesize is 1056 Bytes.

I cross-compiled the ubi tools and my first try to attach was not successful:

$ ./ubiattach /dev/ubi_ctrl -m 6
UBI: attaching mtd6 to ubi0
UBI error: io_init: min. I/O unit (1056) is not power of 2

My question is if it's possible (in general) to get a working version of UBIFS on this kind of flash (with no power of two pagesize)? Anybody ever tried this?

I also tried ubiformat which raises a segfault:

$ ./ubiformat /dev/mtd6
ubiformat: warning!: your MTD system is old and it is impossible to
detect sub-page size. Use -s to get rid of this warning
ubiformat: assume sub-page to be 1056
ubiformat: mtd6 (dataflash), size 4815360 bytes (4.6 MiB), 4560
eraseblocks of 1056 bytes (1.0 KiB), min. I/O size 1056 bytes
libscan: scanning eraseblock 4559 -- 100 % complete
ubiformat: 4554 eraseblocks are supposedly empty
ubiformat: warning!: 6 of 4560 eraseblocks contain non-ubifs data
ubiformat: continue? (yes/no)  yes
ubiformat: warning!: only 0 of 4560 eraseblocks have valid erase counter
ubiformat: erase counter 0 will be used for all eraseblocks
ubiformat: note, arbitrary erase counter value may be specified using -e
option
ubiformat: continue? (yes/no)  yes
ubiformat: use erase counter 0 for all eraseblocks
ubiformat: formatting eraseblock 4559 -- 100 % complete
Segmentation fault

Any comments on this are highly appreciated.

Yeah, I had a feeling we should not have assumed power of 2. But it was so appealing, because we can avoid (slow) divisions when aligning data to min. I/O unit boundary. I knew about DataFlash, but it is usually so small that I did not expect anyone using UBIFS there.

Are you sure you want ubifs on such a tiny flash? We were really targeting to larger ones, say, starting from 64MiB at least.

Basically, there is not fundamental reasons not to support non-power of 2 min. I/O unit size, besides of optimizations. And to fix this, one would need to carefully look at / grep for min_io_size usage in both UBI/UBIFS, and change stuff like ALIGN(x, c->min_io_size) to something else. But there are very many of such places.

Hi Artem,

thanks for your prompt reply.

Quoted 5 lines · Artem Bityutskiy

Yeah, I had a feeling we should not have assumed power of 2. But it was so appealing, because we can avoid (slow) divisions when aligning data to min. I/O unit boundary. I knew about DataFlash, but it is usually so small that I did not expect anyone using UBIFS there.

Quoted 3 lines

Are you sure you want ubifs on such a tiny flash? We were really targeting to larger ones, say, starting from 64MiB at least.

Mmh, the idea to run UBIFS came up due to a problem with JFFS2 on this device. So I wanted to use another writeable flash fs to find out whether its a fs-problem or a mtd/dataflash one.

So you suggest to stick with JFFS2 in this case?

Quoted 1 line

Any comments on this are highly appreciated.

Yeah, I need to make ubiformat nicely return error instead of dying.