linux-kernel - Re: [PATCH] mtd: spi-nor: Fix the number of bytes for the dummy cycles

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Date:   Sun, 6 Nov 2022 23:54:06 +0100
From:   Pratyush Yadav <pratyush@...nel.org>
To:     Allen-KH Cheng <allen-kh.cheng@...iatek.com>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Michael Walle <michael@...le.cc>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        Bayi Cheng <bayi.cheng@...iatek.com>
Subject: Re: [PATCH] mtd: spi-nor: Fix the number of bytes for the dummy
 cycles

On 31/10/22 08:46PM, Allen-KH Cheng wrote:
> The number of bytes used by spi_nor_spimem_check_readop() may be
> incorrect for the dummy cycles. Since nor->read_dummy is not initialized
> before spi_nor_spimem_adjust_hwcaps().
> 
> We use both mode and wait state clock cycles instead of nor->read_dummy.
> 
> Fixes: 0e30f47232ab ("mtd: spi-nor: add support for DTR protocol")
> Co-developed-by: Bayi Cheng <bayi.cheng@...iatek.com>
> Signed-off-by: Bayi Cheng <bayi.cheng@...iatek.com>
> Signed-off-by: Allen-KH Cheng <allen-kh.cheng@...iatek.com>
> ---
>  drivers/mtd/spi-nor/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 6c921eb3fadb..8b9c318a0ad4 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -1914,7 +1914,8 @@ static int spi_nor_spimem_check_readop(struct spi_nor *nor,
>  	spi_nor_spimem_setup_op(nor, &op, read->proto);
>  
>  	/* convert the dummy cycles to the number of bytes */
> -	op.dummy.nbytes = (nor->read_dummy * op.dummy.buswidth) / 8;
> +	op.dummy.nbytes = (read->num_mode_clocks + read->num_wait_states) *
> +			  op.dummy.buswidth / 8;

Good catch!

Reviewed-by: Pratyush Yadav <pratyush@...nel.org>

>  	if (spi_nor_protocol_is_dtr(nor->read_proto))
>  		op.dummy.nbytes *= 2;
>  
> -- 
> 2.18.0
> 

-- 
Regards,
Pratyush Yadav