Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
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>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        Carlo Caione <carlo@caione.org>,
        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>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <1542386439-30166-1-git-send-email-jianxin.pan@amlogic.com>
 <1542386439-30166-3-git-send-email-jianxin.pan@amlogic.com>
 <20181207102456.1dc67e07@xps13>
 <823825a3-86fb-9a20-ae29-85cc52d44093@amlogic.com>
 <20181210123809.5ade45c4@bbrezillon>
 <79a797c2-f37f-7f7c-e907-2d3c2283ec2d@amlogic.com>
 <20181210155057.38788656@xps13>
From:   Liang Yang <liang.yang@amlogic.com>
Message-ID: <d60bac6f-732d-0ddc-2644-17f650dfa885@amlogic.com>
Date:   Tue, 11 Dec 2018 09:56:25 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:60.0) Gecko/20100101
 Thunderbird/60.3.2
MIME-Version: 1.0
In-Reply-To: <20181210155057.38788656@xps13>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

> Thanks,
> Miquèl
> 
> .
>