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

[Heiko Schocher]

Hello Boris,

Am 21.04.2016 um 10:58 schrieb Boris Brezillon:
> On Tue,  2 Feb 2016 11:54:35 +0100
> Heiko Schocher <hs at denx.de> wrote:
>
>> 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.
>
> I ran into the same problem, and produced the exact same patch to
> fix it, so
>
> Reviewed-by: Boris Brezillon <boris.brezillon at free-electrons.com>

Thanks!

I did not yet found time, to investigate this problem deeper,
sorry.

The real reason to me seems, on an empty nand flash, we call
scan_all() which calls scan_peb() which calls ubi_io_read_ec_hdr()
which returns UBI_IO_FF as the nand is empty.

This adds the PEB to the erase list, and here comes the difference
between U-Boot and linux, we have no threads in U-Boot, so we call
the erase_worker function immediately ... which increments the
"ubi->free_count" variable ... after that it get set to
"ubi->free_count = 0" ... which leads into the error we see ...

No idea, if the correct fix not would be to move this erase_worker
call after the attach phase ended, as Richard suggested, or if this
fix is also valid ...

Do you have some time to check such a fix as Richard suggested?

bye,
Heiko
>
>>
>> Signed-off-by: Heiko Schocher <hs at denx.de>
>> ---
>> added Richard to this EMail, as maybe this could be a problem
>> in linux too ... ?
>>
>>   drivers/mtd/ubi/wl.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
>> index 507b091..e823ca5 100644
>> --- a/drivers/mtd/ubi/wl.c
>> +++ b/drivers/mtd/ubi/wl.c
>> @@ -1528,6 +1528,7 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
>>   		INIT_LIST_HEAD(&ubi->pq[i]);
>>   	ubi->pq_head = 0;
>>
>> +	ubi->free_count = 0;
>>   	list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
>>   		cond_resched();
>>
>> @@ -1546,7 +1547,6 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
>>   		found_pebs++;
>>   	}
>>
>> -	ubi->free_count = 0;
>>   	list_for_each_entry(aeb, &ai->free, u.list) {
>>   		cond_resched();
>>
>
>
>

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