Hello Boris,
Am 21.04.2016 um 12:25 schrieb Boris Brezillon:
Hi Heiko,
On Thu, 21 Apr 2016 12:09:34 +0200
Heiko Schocher <[email protected]> wrote:
Hello Boris,
Am 21.04.2016 um 10:58 schrieb Boris Brezillon:
On Tue, 2 Feb 2016 11:54:35 +0100
Heiko Schocher <[email protected]> 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 <[email protected]>
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 ...
I discussed that with Richard, and I think moving the ->free_count
assignment before iterating over the ->erase list is a good solution.
Ah! Ok, than its fine for me too.
I know the Linux code is assuming that the UBI thread is not launched
yet when we call ubi_wl_init(), but to me it seems a bit risky to rely
on this assumption (what if we do the UBI thread creation a bit
earlier for some reason?). And, of course, as you explained, uboot does
not know anything about threads, so all UBI works are executed
synchronously, which makes this implementation buggy in uboot.
Hmm... is it also a valid fix for linux then?
Do you have some time to check such a fix as Richard suggested?
Hm, IMO it complicates the whole implementation for no real benefit,
but I'll let Richard answer that one.
Ok, thanks for your efforts.
bye,
Heiko
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