linux-kernel - Re: [PATCH v2 09/14] mtd: rawnand: qcom: modify write

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Date:   Tue, 22 May 2018 12:02:31 +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 09/14] mtd: rawnand: qcom: modify write_oob to remove
 read codeword part

Hi Abhishek,

Some nitpicking below.

On Thu,  3 May 2018 17:50:36 +0530, Abhishek Sahu
<absahu@...eaurora.org> wrote:

> QCOM NAND layout protect available OOB data bytes with ECC also so

           ^controller

> when ecc->write_oob (qcom_nandc_write_oob) is being called then it

You can just state "->write_oob()"

> can't update just OOB bytes. Currently, it first reads the last
> codeword which includes old OOB bytes. Then it updates the old OOB
> bytes with new one and then again writes the codeword back.

                 ones?

> The reading codeword is unnecessary since all the other bytes
> should be 0xff only.

                                      since the user is responsible to
have these bytes cleared to 0xFF.

> 
> This patch removes the read part and updates the oob bytes with

s/oob/OOB/

> all other data bytes as 0xff.

The end of the sentence is not clear for me. Do you mean that padding
with 0xFF is realized before write?

> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
> * Changes from v1:
> 
>  NEW CHANGE
> 
>  drivers/mtd/nand/raw/qcom_nandc.c | 17 +++++------------
>  1 file changed, 5 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
> index 61d0e7d..f85d8ab 100644
> --- a/drivers/mtd/nand/raw/qcom_nandc.c
> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
> @@ -2067,10 +2067,9 @@ static int qcom_nandc_write_page_raw(struct mtd_info *mtd,
>   * implements ecc->write_oob()
>   *
>   * the NAND controller cannot write only data or only oob within a codeword,

s/oob/OOB/

Remove the trailing ','

> - * since ecc is calculated for the combined codeword. we first copy the
> - * entire contents for the last codeword(data + oob), replace the old oob
> - * with the new one in chip->oob_poi, and then write the entire codeword.
> - * this read-copy-write operation results in a slight performance loss.
> + * since ecc is calculated for the combined codeword. So make all the data

s/ecc/ECC/

> + * bytes as 0xff and update the oob from chip->oob_poi, and then write
> + * the entire codeword again.

What about "Pad the data area with OxFF before writing."?

>   */
>  static int qcom_nandc_write_oob(struct mtd_info *mtd, struct nand_chip *chip,
>  				int page)
> @@ -2082,20 +2081,14 @@ static int qcom_nandc_write_oob(struct mtd_info *mtd, struct nand_chip *chip,
>  	int data_size, oob_size;
>  	int ret;
>  
> -	host->use_ecc = true;
> -
> -	clear_bam_transaction(nandc);
> -	ret = copy_last_cw(host, page);
> -	if (ret)
> -		return ret;
> -
> -	clear_read_regs(nandc);
>  	clear_bam_transaction(nandc);
>  
>  	/* calculate the data and oob size for the last codeword/step */
>  	data_size = ecc->size - ((ecc->steps - 1) << 2);
>  	oob_size = mtd->oobavail;
> +	host->use_ecc = true;

You don't need to move this line here, do you?

>  
> +	memset(nandc->data_buffer, 0xff, host->cw_data);
>  	/* override new oob content to last codeword */
>  	mtd_ooblayout_get_databytes(mtd, nandc->data_buffer + data_size, oob,
>  				    0, mtd->oobavail);


Once fixed, you can add my:

Acked-by: Miquel Raynal <miquel.raynal@...tlin.com>

Thanks,
Miquèl