linux-kernel - Re: [PATCH v2 06/14] mtd: rawnand: qcom: erased page detection for uncorrectable errors only

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Date:   Tue, 22 May 2018 19:40:21 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Boris Brezillon <boris.brezillon@...tlin.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, Andy Gross <andy.gross@...aro.org>,
        Archit Taneja <architt@...eaurora.org>
Subject: Re: [PATCH v2 06/14] mtd: rawnand: qcom: erased page detection for
 uncorrectable errors only

On 2018-05-22 12:34, Miquel Raynal wrote:
> Hi Abhishek,
> 
> On Thu,  3 May 2018 17:50:33 +0530, Abhishek Sahu
> <absahu@...eaurora.org> wrote:
> 
>> Following is the flow in the HW if controller tries to read erased
>> page
> 
> Nit:  ^ missing ':'
> 

  Sure. I will fix this.

>> 
>> 1. First ECC uncorrectable error will be generated from ECC engine
>>    since ECC engine first calculates the ECC with all 0xff and match
>>    the calculated ECC with ECC code in OOB (which is again all 0xff).
>> 2. After getting ECC error, erased CW detection logic will be
>>    applied which is different for BCH and RS ECC
>>     a. For BCH, HW checks if all the bytes in page are 0xff and then
>>        it updates the status in separate register
>>        NAND_ERASED_CW_DETECT_STATUS.
>>     b. For RS ECC, the HW reports the same error when reading an
>>        erased CW, but it notifies that it is an erased CW by
>>        placing special characters at certain offsets in the
>>        buffer.
>> 
>> So the erased CW detect status should be checked only if ECC engine
>> generated the uncorrectable error.
>> 
>> Currently for all other operational errors also (like TIMEOUT, MPU
>> errors, etc.), the erased CW detect logic is being applied so fix this
>> and return EIO for other operational errors.
>> 
>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
>> ---
>> * Changes from v1:
>> 
>>   1. Added more detail in commit message
>>   2. Added comment before each if/else
> 
> Thanks for that, it's much more ease to review :)

  Thanks Miquel for your review.

  Regards,
  Abhishek

> 
>>   3. Removed redundant check for BS_UNCORRECTABLE_BIT
>> 
>>  drivers/mtd/nand/raw/qcom_nandc.c | 65 
>> ++++++++++++++++++++++++++-------------
>>  1 file changed, 43 insertions(+), 22 deletions(-)
>> 
> 
> Acked-by: Miquel Raynal <miquel.raynal@...tlin.com>
> 
> Thanks,
> Miquèl