linux-kernel - Re: [PATCH v14 08/15] mtd: spi-nor: core: enable octal DTR mode when possible

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Message-ID: <3e162719-80c7-03dc-dc2a-29a46bc4cb2c@microchip.com>
Date:   Thu, 1 Oct 2020 08:09:14 +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 v14 08/15] mtd: spi-nor: core: enable octal DTR mode when
 possible

On 9/30/20 9:57 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 73a26e7e32c2..6b54a923002a 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -3068,6 +3068,35 @@ 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);

Ideally patch 9/15 and 10/15 should have been before 8/15. We should deny
the access to octal dtr enable for NV flashes since moment 0.

> +       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 Quad I/O if needed.
>   * @nor:                pointer to a 'struct spi_nor'
> @@ -3107,6 +3136,12 @@ 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);
>         if (err) {
>                 dev_dbg(nor->dev, "quad mode not supported\n");
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index 9a33c8d07335..5cfe2db9ee13 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -203,6 +203,7 @@ struct spi_nor_locking_ops {
>   *                      higher index in the array, the higher priority.
>   * @erase_map:         the erase map parsed from the SFDP Sector Map Parameter
>   *                      Table.
> + * @octal_dtr_enable:  enables SPI NOR octal DTR mode.
>   * @quad_enable:       enables SPI NOR quad mode.
>   * @set_4byte_addr_mode: puts the SPI NOR in 4 byte addressing mode.
>   * @convert_addr:      converts an absolute address into something the flash
> @@ -226,6 +227,7 @@ struct spi_nor_flash_parameter {
> 
>         struct spi_nor_erase_map        erase_map;
> 
> +       int (*octal_dtr_enable)(struct spi_nor *nor, bool enable);
>         int (*quad_enable)(struct spi_nor *nor);
>         int (*set_4byte_addr_mode)(struct spi_nor *nor, bool enable);
>         u32 (*convert_addr)(struct spi_nor *nor, u32 addr);
> --
> 2.28.0
>