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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>,
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From:   Liang Yang <liang.yang@amlogic.com>
Message-ID: <356aed95-518d-7cd0-4337-184f181472ad@amlogic.com>
Date:   Tue, 11 Dec 2018 16:36:47 +0800
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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.

> 
> Thanks,
> Miquèl
> 
> .
>