[BUG] emmc `env erase` erase unrelated data

Tom Rini trini at konsulko.com
Mon Nov 29 16:43:03 CET 2021

On Mon, Nov 29, 2021 at 04:38:34PM +0100, Francesco Dolcini wrote:
> Hello Tom,
> On Mon, Nov 29, 2021 at 10:25:30AM -0500, Tom Rini wrote:
> > On Mon, Nov 29, 2021 at 02:21:23PM +0100, Francesco Dolcini wrote:
> > > I noticed an issue with env erase command when environment is stored in a
> > > emmc device, in case start/end are not aligned to the emmc erase groups
> > > size additional data is erased with just a warning.
> ...
> > > I do not think that this is the correct behavior, I think that in case
> > > the env is not aligned to the erase block size the erase should either
> > > fail or fall back to just writing 0xff. Not sure if just changing
> > > `mmc_berase()` is going to affect any other use case in which is valid
> > > to have a non-aligned start/size and just erase around it after a
> > > warning.
> > 
> > Largely intentional behavior.  Perhaps the help text at least should be
> > updated to note that environment size for MMC needs to be a multiple of
> > erase block size?  And further that when using redundant environment
> > it's strongly encouraged to make sure each environment is on its own
> > erase block.
> I'm not really convinced, but let's move forward from this point.

Alright.  I'll also agree that it was designed when erase blocks were
probably smaller and that yes, it's a lot more wasteful these days.

> Are you aware of any other issues in case the emmc environment is not a
> multiple/aligned to the erase size? I believe that the rest of the code
> just read/write to it, so once it is aligned to the read/write block
> size (512 bytes, usually) there should be no problem.

I believe you're correct.

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