linux-kernel - Re: [PATCH v2 4/6] spi: spi-mem: reject partial cycle transfers in 8D-8D-8D mode

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Message-ID: <0e22270e-7c4a-9ba3-e468-963d21ab63a0@microchip.com>
Date:   Thu, 23 Dec 2021 11:43:06 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...com>, <michael@...le.cc>, <miquel.raynal@...tlin.com>,
        <richard@....at>, <vigneshr@...com>, <broonie@...nel.org>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>
Subject: Re: [PATCH v2 4/6] spi: spi-mem: reject partial cycle transfers in
 8D-8D-8D mode

On 5/31/21 9:17 PM, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> In 8D-8D-8D mode two bytes are transferred per cycle. So an odd number
> of bytes cannot be transferred because it would leave a residual half
> cycle at the end. Consider such a transfer invalid and reject it.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> Reviewed-by: Mark Brown <broonie@...nel.org>
> 
> ---
> 
> Changes in v2:
> - Add Mark's R-by (spell corrected).
> 
>  drivers/spi/spi-mem.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 1513553e4080..ab9eefbaa1d9 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -162,7 +162,17 @@ static bool spi_mem_check_buswidth(struct spi_mem *mem,
>  bool spi_mem_dtr_supports_op(struct spi_mem *mem,
>                              const struct spi_mem_op *op)
>  {
> -       if (op->cmd.nbytes != 2)
> +       if (op->cmd.buswidth == 8 && op->cmd.nbytes % 2)

!IS_ALIGNED(op->cmd.nbytes, 2)?

> +               return false;
> +
> +       if (op->addr.nbytes && op->addr.buswidth == 8 && op->addr.nbytes % 2)
> +               return false;
> +
> +       if (op->dummy.nbytes && op->dummy.buswidth == 8 && op->dummy.nbytes % 2)
> +               return false;
> +
> +       if (op->data.dir != SPI_MEM_NO_DATA &&
> +           op->dummy.buswidth == 8 && op->data.nbytes % 2)

dummy is sent on the same buswidth as data's indeed, but I would
s/op->dummy.buswidth/op->data.buswidth for code consistency reasons.

>                 return false;
> 
>         return spi_mem_check_buswidth(mem, op);
> --
> 2.30.0
>