linux-kernel - Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller

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Date:   Tue, 11 Dec 2018 09:56:25 +0800
From:   Liang Yang <liang.yang@...ogic.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Boris Brezillon <boris.brezillon@...tlin.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        <linux-mtd@...ts.infradead.org>, Yixun Lan <yixun.lan@...ogic.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh@...nel.org>, Jian Hu <jian.hu@...ogic.com>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND
 flash controller

Hi Miquel,

On 2018/12/10 22:50, Miquel Raynal wrote:
> Hi Liang,
> 
> Liang Yang <liang.yang@...ogic.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@...ogic.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.

> Thanks,
> Miquèl
> 
> .
>