[PATCH RFC] Alphascale ASM9260 NAND controller driver

[Oleksij Rempel]

Am 17.12.2014 um 15:36 schrieb Oleksij Rempel:
> Am 17.12.2014 um 14:24 schrieb Boris Brezillon:
>> Hi Oleksij,
>>
>> On Wed, 17 Dec 2014 12:45:17 +0100
>> Oleksij Rempel <linux at rempel-privat.de> wrote:
>>
>>> I collected some questions with this driver. It will be great if you
>>> can help me:
>>> * Do HW_ECC driver should provideo option for SW_ECC?
>>
>> This is not mandatory. I did it in the sunxi driver for testing
>> purpose, but it should work fine without it.
>>
>>> * My HW do ECC correction for n-bits per 512B, it mean it will
>>> split block in 512B parts. If one of part has uncorrectable error, complete block will be
>>> reported as failed. Are there any way for partial recovery?
>>
>> I think what you're calling block here is actually a page.
>> Regarding your question, there is no way to recover part of a page, but
>> each ECC block should be tested and max_bitflip should be returned
>> (even if some ECC blocks contains too many errors to be corrected).
>> Take a look at [1] for an example.
> 
> From Flash point of view block or part which i mean != page. In my case
> it is TOSHIBA TC58NVG0S3ETA00, organized as (2048 + 64) bytes × 64 pages
> × 1024blocks. The NFC will split each each 2048B page to 512B
> blocks/???/parts/sub_page/ecc_step/better_name.
> 
> HW_ECC provide bit_flip counter for each sub_page. If all sub_pages are
> recovered, there is no problem. Beside the question, how many bit should
> be counted. Right now max_bitflips = sum(all_sub_pages).

Ok, i understood. max_bitflips = sum(all_sub_pages) makes no sense,
since it is not indicating actual pre fail state of one eccstep/subpage.

> Second problem which i have is that, there is only one ecc_error flag
> for all sub_pages. If one sub_page filed, i don't know which one. Ecc
> erroc counter register can't help here. Only way is to reread complete
> page with SW_ECC.
> 
>>> * This HW reports count of ECC bitflips for each part. Do i need to return count of errors on
>>> all parts for one block?
>>
>> Again: block == page, and no, you should only return the maximum
>> corrected bitflips (same example [1]).
>>
>>
>>> * If HW_ECC different stranges, how it should be configured? With DT or automatically
>>> calculated?
>>
>> I don't get that one...
>> Are you talking about ECC requirements (ECC strength and steps) ?
> 
> Yes. Well, i can't choice ECC step(it is 512B on this HW), only strange.
> 
>> Best Regards,
>>
>> Boris
>>
>> [1]http://lxr.free-electrons.com/source/drivers/mtd/nand/nand_base.c#L1157
>>
> 
> 
> 
> 
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-- 
Regards,
Oleksij

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