On Wed, 2018-11-21 at 08:56 +0100, Sascha Hauer wrote: > Hi Matthias, > > On Tue, Nov 20, 2018 at 10:40:34AM +0100, > matthias.schiffer@xxxxxxxxxxxxxxx wrote: > > From: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> > > > > Devices like MRAM do not need to be erased; in fact, trying to do a > > partial > > erase will fail with -EINVAL, as they don't have a proper erase > > block size > > defined. > > Where does this -EINVAL come from? Wouldn't it be an option to check > for > the MTD_NO_ERASE flag mtd_op_erase() and return -EOPNOTSUPP there? > > Sascha > Hmm, what are the expected semantics of MTD_NO_ERASE - "does not need erase" or "does not support erase"? According to code comments, it's the former. The MRAM I'm working with reports an erase size equal to its total size: barebox:/ devinfo m25p0 Parameters: erasesize: 131072 (type: uint32) oobsize: 0 (type: uint32) partitions: 128k(barebox-environment) (type: string) size: 131072 (type: uint64) writesize: 1 (type: uint32) This matches what Linux reports, but it seems to me that this MRAM does not actually implement it: When I try to erase the whole flash (from Linux or Barebox), it does return success, but the data is unchanged. When I configure the environment to span the whole flash, envfs_save() is working fine without my patch, as the erase is successful. The problems start when I try to partition the MRAM, as envfs_save() will now try to erase a block smaller than the erasesize, leading to -EINVAL. I'm not sure if making mtd_op_erase() check for MTD_NO_ERASE is the correct solution - it would obviously be fine for my MRAM, as erase is a noop anyways, but I have no idea if there are other devices that set the flag, but do support erase (and just don't need it for normal write operations). Anyways, I have no problem with implementing the fix that way if we decide that these are the semantics we want. Matthias _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
