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

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Message-ID: <20180522090459.71d35004@xps13>
Date:   Tue, 22 May 2018 09:04:59 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Abhishek Sahu <absahu@...eaurora.org>
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

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 ':'

> 
> 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 :)

>   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