[U-Boot] [PATCH] mtd, ubi: set free_count to zero before walking through erase list

[Heiko Schocher <hs@denx.de>]

Hello Richard,

Am 02.02.2016 um 12:40 schrieb Richard Weinberger:
> Am 02.02.2016 um 11:54 schrieb Heiko Schocher:
>> Set free_count to zero before walking through ai->erase list
>> in wl_init().
>>
>> As U-Boot has no workqueue/threads, it immediately calls
>> erase_worker(), which increase for each erased block
>> free_count. Without this patch, free_count gets after
>> this initialized to zero in wl_init(), so the free_count
>> variable always has the maybe wrong value 0.
>>
>> Detected this behaviour on the dxr2 board, where the
>> UBI fastmap gets not written when attaching/dettaching
>> on an empty NAND. It drops instead the error message:
>>
>> could not find any anchor PEB
>>
>> With this patch, fastmap gets written on dettach.
>>
>> Signed-off-by: Heiko Schocher <hs@denx.de>
>> ---
>> added Richard to this EMail, as maybe this could be a problem
>> in linux too ... ?
>
> ubi_wl_init() is called by ubi_attach().

Yes, exactly, same for U-Boot.

> So, as soon your UBI image is attached the WL subsystem
> is fully initialized and ready to use.
> If you try to use it before you're in undefined state.
> u-boot must not run the erase_worker() before the attach
> phase is done.

ubi_attach() in drivers/mtd/ubi/attach.c calls
ubi_wl_init() in drivers/mtd/ubi/wl.c. There schedule_erase() is
called, which calls schedule_ubi_work(). same for linux
and U-Boot ...

Now the U-Boot special:
In U-Boot we have no threads, so in U-Boot this "work" is done
immediately...

Which means in this case, that erase_worker() is executed immediately,
so before ubi_attach() finished ... but couldn;t it be that
with schedule_work(), the erase_work() couldn;t be exeucted before
ubi_attach() is finished?

> Do you have more details what exactly happened?
> This needs a deeper investigation.

I came into this errorcase if the nand flash is empty. Hmm... why
is there erase work? I try to find out more.

bye,
Heiko
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