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Subject: Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND
 flash controller
To:     Miquel Raynal <miquel.raynal@bootlin.com>
CC:     Boris Brezillon <boris.brezillon@bootlin.com>,
        Jianxin Pan <jianxin.pan@amlogic.com>,
        <linux-mtd@lists.infradead.org>, Yixun Lan <yixun.lan@amlogic.com>,
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        Kevin Hilman <khilman@baylibre.com>,
        Rob Herring <robh@kernel.org>, Jian Hu <jian.hu@amlogic.com>,
        Hanjie Lin <hanjie.lin@amlogic.com>,
        Victor Wan <victor.wan@amlogic.com>,
        <linux-amlogic@lists.infradead.org>,
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 <356aed95-518d-7cd0-4337-184f181472ad@amlogic.com>
 <20181211100718.51d2cd6c@xps13>
From:   Liang Yang <liang.yang@amlogic.com>
Message-ID: <ce821991-423b-837a-a936-699716791aad@amlogic.com>
Date:   Tue, 11 Dec 2018 17:43:11 +0800
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Hi Miquel,

On 2018/12/11 17:07, Miquel Raynal wrote:
> Hi Liang,
> 
> Liang Yang <liang.yang@amlogic.com> wrote on Tue, 11 Dec 2018 16:36:47
> +0800:
> 
>> Hi Miquel,
>>
>> Thanks for your quickly reply.
>>
>> On 2018/12/11 15:54, Miquel Raynal wrote:
>>> Hi Liang,
>>>
>>> Liang Yang <liang.yang@amlogic.com> wrote on Tue, 11 Dec 2018 09:56:25
>>> +0800:
>>>    
>>>> Hi Miquel,
>>>>
>>>> On 2018/12/10 22:50, Miquel Raynal wrote:
>>>>> Hi Liang,
>>>>>
>>>>> Liang Yang <liang.yang@amlogic.com> wrote on Mon, 10 Dec 2018 20:12:39
>>>>> +0800:
>>>>>     >>>> On 2018/12/10 19:38, Boris Brezillon wrote:
>>>>>>> On Mon, 10 Dec 2018 19:23:46 +0800
>>>>>>> Liang Yang <liang.yang@amlogic.com> wrote:
>>>>>>>      >>>>>> +			mtd->ecc_stats.failed++;
>>>>>>>>>> +			continue;
>>>>>>>>>> +		}
>>>>>>>>>> +		mtd->ecc_stats.corrected += ECC_ERR_CNT(*info);
>>>>>>>>>> +		bitflips = max_t(u32, bitflips, ECC_ERR_CNT(*info));
>>>>>>>>>> +	}
>>>>>>>>>
>>>>>>>>> Are you sure you handle correctly empty pages with bf?
>>>>>>>>>       >> if scramble is enable, i would say yes here.
>>>>>>>> when scramble is disabled, i am considering how to use the helper
>>>>>>>> nand_check_erased_ecc_chunk, but it seems that i can't get the ecc
>>>>>>>> bytes which is caculated by ecc engine.by the way, nfc dma doesn't send
>>>>>>>> out the ecc parity bytes.
>>>>>>>
>>>>>>> Even if the ECC engine is disabled?
>>>>>>>      >> No.
>>>>>> When ECC engine is disabled, it can read the ecc parity bytes ; but there is another problem that i need to consider how code struct looks better when reading error with ecc opened and then try to raw read.
>>>>>> Is there a good idea?
>>>>>
>>>>> When reading with ECC enabled, in case of uncorrectable error you
>>>>> must re-read without ECC, then check if the page is empty or not with
>>>>> the core helpers (nand_check_erased_*()).
>>>>>
>>>>> Is this what you meant?
>>>>>     >> yes. when uncorrectable ECC error, i need firstly read out the ECC bytes without ECC engine and then use the helper nand_check_erased_ecc_chunk to check if blank page.
>>>> Of course, the precondition is without scrambler, or the bland page can be detected by meson NFC.
>>>
>>> A suppose you meant "blank page"? If yes, then you don't need the
>>> helper to check for only-0xFF pages. If the controller tells you if the
>>> page was blank, then just check for that bit.
>>>    
>>
>> i think not. we need to return back the previous problem that how i can get the bitflips of one blank page. i think i need the helper.
> 
> You are right, I suppose the "blank page" flag is only triggered if
> there is no bitflip. In this case you can assume there are no
> bitflips. Otherwise the controller will trigger an
> uncorrectable error event and you will have to re-read the page
> without ECC and check for bitflips with the helper.
> 
yes, that is right. i will do the "re-read" process.
> 
> Thanks,
> Miquèl
> 
> .
>