Re: [PATCH v4 0/2] mtd: hisilicon: add a new driver for NAND controller of hisilicon hip04 Soc

[Zhou Wang <wangzhou.bry@gmail.com>]

On 2014年12月17日 09:03, Brian Norris wrote:
> On Thu, Dec 11, 2014 at 08:02:27PM +0800, Zhou Wang wrote:
>> On 2014年11月30日 17:08, Brian Norris wrote:
>>> Have you tested on the MTD test modules (drivers/mtd/tests/*)? This is
>>> important, as we seem to regularly get UBIFS bug reports from users
>>> whose drivers have not even passed some of the simple tests.
>>>
>>> Also, it might be worth testing out the UBI tests found in the mtd-utils
>>> package.
>>
>> I have tested this NAND controller driver on the MTD test modules
>> (drivers/mtd/tests/*). All tests passed except mtd_nandbiterrs.ko.
>>
>> Here is the test log for mtd_nandbiterrs:
>> /home # insmod mtd_nandbiterrs.ko dev=2 page_offset=1 seed=110 mode=0
>> [  100.484995]
>> [  100.490082] ==================================================
>> [  100.509657] mtd_nandbiterrs: MTD device: 2
>> [  100.523413] mtd_nandbiterrs: MTD device size 8388608,
>> eraseblock=131072, page=2048, oob=64
>> [  100.551134] mtd_nandbiterrs: Device uses 2 subpages of 1024 bytes
>> [  100.571585] mtd_nandbiterrs: Using page=1, offset=2048, eraseblock=0
>> [  104.431136] mtd_nandbiterrs: incremental biterrors test
>> [  104.448872] mtd_nandbiterrs: write_page
>> [  104.463193] mtd_nandbiterrs: rewrite page
>> [  104.477620] mtd_nandbiterrs: read_page
>> [  104.490898] mtd_nandbiterrs: verify_page
>> [  104.504338] mtd_nandbiterrs: Successfully corrected 0 bit errors
>> per subpage
>> [  104.527985] mtd_nandbiterrs: Inserted biterror @ 0/5
>> [  104.544673] mtd_nandbiterrs: Inserted biterror @ 1024/2
>> [  104.562197] mtd_nandbiterrs: rewrite page
>> [  104.576766] mtd_nandbiterrs: read_page
>> [  104.590052] mtd_nandbiterrs: verify_page
>> [  104.603252] mtd_nandbiterrs: Error: page offset 0, expected 23, got 03
>> [  104.625203] mtd_nandbiterrs: Error: page offset 1024, expected 06, got 02
>> [  104.648056] mtd_nandbiterrs: ECC failure, read data is incorrect
>> despite read success
>> insmod: can't insert 'mtd_nandbiterrs.ko': Input/output error
>>
>> The reason for above failure is that:
>> In ECC mode, when rewriting page data to NAND flash, the NAND
>> controller will also produce ECC code and write them to NAND flash
>> as well. So when we read data from NAND flash, there is no need to
>> correct the error bit. We read what we write to the flash.
>>
>> In mtd_nandbiterrs test, We call nand_write_page_raw indeed to perform
>> rewrite operation. My question is that: in this NAND controller hardware
>> design, it is hard to implement hardware specific write_page_raw to
>> write page data without producing ECC code, will this bring some bad
>> effects somewhere? It will be very nice if you and anyone can give
>> me some advice.
>
> As of now, read_page_raw()/write_page_raw() are not required for any
> normal operation. They are useful for debugging and testing though, with
> tests like this one.
>
> In the future, we might use read_page_raw() for implementing (optional)
> software-based detection of blank/erased pages that have bitflips in
> them -- i.e., all 0xff but with a few bitflips. See:
>
>    http://lists.infradead.org/pipermail/linux-mtd/2014-December/056749.html
>    http://article.gmane.org/gmane.linux.drivers.mtd/52183/
>
> Brian
>

Got it, thanks for your explanation, Brian. I will resend the new
version of patchset based on v3.19-rc1 later.

Regards,
Zhou