linux-kernel - Re: [PATCH v13 09/15] mtd: spi-nor: core: enable octal DTR mode when possible

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Message-ID: <feb046fd-a9ea-9ea3-55f7-bf823ed1e61f@microchip.com>
Date:   Tue, 29 Sep 2020 11:26:25 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...com>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <nsekhar@...com>, <boris.brezillon@...labora.com>
Subject: Re: [PATCH v13 09/15] mtd: spi-nor: core: enable octal DTR mode when
 possible

Hi,

On 9/16/20 3:44 PM, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Allow flashes to specify a hook to enable octal DTR mode. Use this hook
> whenever possible to get optimal transfer speeds.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  drivers/mtd/spi-nor/core.c | 35 +++++++++++++++++++++++++++++++++++
>  drivers/mtd/spi-nor/core.h |  2 ++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 87c568debf14..6ee93544d72f 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -3069,6 +3069,35 @@ static int spi_nor_init_params(struct spi_nor *nor)
>         return 0;
>  }
> 
> +/** spi_nor_octal_dtr_enable() - enable Octal DTR I/O if needed
> + * @nor:                 pointer to a 'struct spi_nor'
> + * @enable:              whether to enable or disable Octal DTR
> + *
> + * Return: 0 on success, -errno otherwise.
> + */
> +static int spi_nor_octal_dtr_enable(struct spi_nor *nor, bool enable)
> +{
> +       int ret;
> +
> +       if (!nor->params->octal_dtr_enable)
> +               return 0;
> +
> +       if (!(nor->read_proto == SNOR_PROTO_8_8_8_DTR &&
> +             nor->write_proto == SNOR_PROTO_8_8_8_DTR))
> +               return 0;
> +
> +       ret = nor->params->octal_dtr_enable(nor, enable);
> +       if (ret)
> +               return ret;
> +
> +       if (enable)
> +               nor->reg_proto = SNOR_PROTO_8_8_8_DTR;
> +       else
> +               nor->reg_proto = SNOR_PROTO_1_1_1;
> +
> +       return 0;
> +}
> +
>  /**
>   * spi_nor_quad_enable() - enable/disable Quad I/O if needed.
>   * @nor:                pointer to a 'struct spi_nor'
> @@ -3109,6 +3138,12 @@ static int spi_nor_init(struct spi_nor *nor)
>  {
>         int err;
> 
> +       err = spi_nor_octal_dtr_enable(nor, true);
> +       if (err) {
> +               dev_dbg(nor->dev, "octal mode not supported\n");
> +               return err;
> +       }
> +
>         err = spi_nor_quad_enable(nor, true);

Is it possible to enable octal dtr and quad at the same time?
Maybe an 'if/else if' here depending on the values of nor->read_proto and
nor->write_proto

Cheers,
ta