linux-kernel - Re: [PATCH 1/3] mtd: rawnand: qcom: Update read

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Date:   Fri, 18 Aug 2023 21:59:08 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Md Sadre Alam <quic_mdalam@...cinc.com>
Cc:     mani@...nel.org, richard@....at, vigneshr@...com,
        linux-mtd@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_srichara@...cinc.com
Subject: Re: [PATCH 1/3] mtd: rawnand: qcom: Update read_loc size to 512

Hi Md,

quic_mdalam@...cinc.com wrote on Fri, 18 Aug 2023 20:20:59 +0530:

> For parameter page read upper layer is passing len
> as 256 bytes and if we try to configure 256 bytes
> size in read loaction register then subsequent bam
> transaction is getting timed out for 4K nand devices.
> So update this length as one step size if its
> less than NANDC_STEP_SIZE.
> 
> Signed-off-by: Sricharan Ramabadhran <quic_srichara@...cinc.com>
> Signed-off-by: Md Sadre Alam <quic_mdalam@...cinc.com>

I'm fine with patches 2 and 3 and will take them. But this one does not
seem legitimate. I don't like it. Are you sure the ECC engine was not
enabled when it timed out? Default should be having the ECC disabled
and it should just get enabled when you need it. There is no reason
why, specifically on NAND devices, it would not be possible to read 256
bytes.

> ---
>  drivers/mtd/nand/raw/qcom_nandc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
> index d4ba0d04c970..413e214c8e87 100644
> --- a/drivers/mtd/nand/raw/qcom_nandc.c
> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
> @@ -2885,6 +2885,9 @@ static int qcom_param_page_type_exec(struct nand_chip *chip,  const struct nand_
>  	op_id = q_op.data_instr_idx;
>  	len = nand_subop_get_data_len(subop, op_id);
>  
> +	if (len < NANDC_STEP_SIZE)
> +		len = NANDC_STEP_SIZE;
> +
>  	nandc_set_read_loc(chip, 0, 0, 0, len, 1);
>  
>  	if (!nandc->props->qpic_v2) {


Thanks,
Miquèl