[U-Boot] Porting UBI fixes (specially fastmap's) to U-Boot

[Richard Weinberger <richard@nod.at>]

Am 19.10.2015 um 23:40 schrieb Ezequiel Garcia:
> On 19 October 2015 at 17:22, Richard Weinberger <richard@nod.at> wrote:
>> Am 19.10.2015 um 15:47 schrieb Ezequiel Garcia:
>>> After some further investigation, printing the counters as Richard suggested
>>> I found it was a bug on my side :-( The Linux partition and the U-Boot partition
>>> had different size (i.e. PEB count) and so Fastmap complained :-(
>>>
>>> We trimmed the Linux partition size, and forgot to change U-Boot's
>>> (or thought it wouldn't matter).
>>>
>>> Sorry for the noise guys!
>>
>> Good to know. :)
>>
>> Let me find a way to detect and report this kind of user error
>> better.
>> The WARN_ON() is only meant for bad internal errors.
>>
> 
> Sure. In case it's not clear, let me clarify what the issue was: the
> MTD partition
> has one size in Linux (4072 EB) and another size in U-Boot (4076 EB).
> 
> When the map was built by Linux's Fastmap, it contained a number of PEBs that
> conflicted with the number of PEBs U-Boot's Fastmap code was expecting
> (becase Linux EB != U-Boot EB).
> 
> Not sure how you would detect such a mismatch, but it was a very good
> idea to print a noisy warning :-)

I think it would make sense to drop the WARN_ON() and replace it to a
warning using ubi_err() which explains what possible went wrong.
i.e. MTD partition layout mismatch, an internal error, etc...

> We were effectively running without fastmap so far, becasue neither U-Boot
> nor Linux could find a proper fastmap and attach the UBI partition using it.

Yeah, U-Boot's fast decided to fall back to scanning mode and had to drop the
existing fastmap and therefore Linux also had to do a full scan too.

Thanks,
//richard