linux-kernel - Re: [PATCH 1/1 v3] driver:mtd:spi-nor: Add quad I/O support for Micron spi nor

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Message-ID: <CAD6G_RQGsLP35E-ecNUvSZyGht4bta4dmnMwLdg+QbEp0bTGmg@mail.gmail.com>
Date:	Thu, 13 Nov 2014 02:29:29 +0530
From:	Jagan Teki <jagannadh.teki@...il.com>
To:	bpqw <bpqw@...ron.com>
Cc:	Marek Vasut <marex@...x.de>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	"geert+renesas@...der.be" <geert+renesas@...der.be>,
	"grmoore@...era.com" <grmoore@...era.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"shijie8@...il.com" <shijie8@...il.com>
Subject: Re: [PATCH 1/1 v3] driver:mtd:spi-nor: Add quad I/O support for
 Micron spi nor

On 27 October 2014 05:39, bpqw <bpqw@...ron.com> wrote:
> This patch adds code which enables Quad I/O mode on Micron SPI NOR flashes.
>
> For Micron SPI NOR flash, enabling or disabling quad I/O protocol is controlled
> by EVCR (Enhanced Volatile Configuration Register), Quad I/O protocol bit 7.
> When EVCR bit 7 is reset to 0, the SPI NOR flash will operate in quad I/O mode.
>
> Signed-off-by: bean huo <beanhuo@...ron.com>
> Acked-by: Marek Vasut <marex@...x.de>
> ---
>  v1-v2:modified to that capture wait_till_ready()
>          return value,if error,directly return its
>          the value.
>  v2-v3:directly use the reurning error value of
>          read_reg and write_reg,instead of -EINVAL.
>
>  drivers/mtd/spi-nor/spi-nor.c |   46 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/mtd/spi-nor.h   |    6 ++++++
>  2 files changed, 52 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index b5ad6be..486b167 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -878,6 +878,45 @@ static int spansion_quad_enable(struct spi_nor *nor)
>         return 0;
>  }
>
> +static int micron_quad_enable(struct spi_nor *nor) {
> +       int ret, val;
> +
> +       ret = nor->read_reg(nor, SPINOR_OP_RD_EVCR, &val, 1);
> +       if (ret < 0) {
> +               dev_err(nor->dev, "error %d reading EVCR\n", ret);
> +               return ret;
> +       }

Best to define read_evsr()

> +
> +       write_enable(nor);
> +
> +       /* set EVCR ,enable quad I/O */
> +       nor->cmd_buf[0] = val & ~EVCR_QUAD_EN_MICRON;
> +       ret = nor->write_reg(nor, SPINOR_OP_WD_EVCR, nor->cmd_buf, 1, 0);
> +       if (ret < 0) {
> +               dev_err(nor->dev,
> +                       "error while writing EVCR register\n");
> +               return ret;
> +       }
> +
> +       ret = wait_till_ready(nor);
> +       if (ret)
> +               return ret;

I don't think this will ready w/o wait time or something - may be use
if (wait_till_ready(nor))
       return 1;

> +
> +       /* read EVCR and check it */
> +       ret = nor->read_reg(nor, SPINOR_OP_RD_EVCR, &val, 1);
> +       if (ret < 0) {
> +               dev_err(nor->dev, "error %d reading EVCR\n", ret);
> +               return ret;
> +       }
> +       if (val & EVCR_QUAD_EN_MICRON) {
> +               dev_err(nor->dev, "Micron EVCR Quad bit not clear\n");
> +               return -EINVAL;
> +       }

IMHO, use read_evcr() as defined above and write the finite statement code like
        ret = read_evcr(nor);
        if (!(ret > 0 && (ret & EVCR_QUAD_EN_MICRON))) {
                dev_err(nor->dev, "Micron EVCR Quad bit not clear\n");
                return -EINVAL;
        }

> +
> +       return 0;
> +}
> +
>  static int set_quad_mode(struct spi_nor *nor, u32 jedec_id)  {
>         int status;
> @@ -890,6 +929,13 @@ static int set_quad_mode(struct spi_nor *nor, u32 jedec_id)
>                         return -EINVAL;
>                 }
>                 return status;
> +       case CFI_MFR_ST:
> +               status = micron_quad_enable(nor);
> +               if (status) {
> +                       dev_err(nor->dev, "Micron quad-read not enabled\n");
> +                       return -EINVAL;
> +               }
> +               return status;
>         default:
>                 status = spansion_quad_enable(nor);
>                 if (status) {
> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h index 9e6294f..d71b659 100644
> --- a/include/linux/mtd/spi-nor.h
> +++ b/include/linux/mtd/spi-nor.h
> @@ -56,6 +56,10 @@
>  /* Used for Spansion flashes only. */
>  #define SPINOR_OP_BRWR         0x17    /* Bank register write */
>
> +/* Used for Micron flashes only. */
> +#define SPINOR_OP_RD_EVCR      0x65    /* Read EVCR register */
> +#define SPINOR_OP_WD_EVCR      0x61    /* Write EVCR register */
> +
>  /* Status Register bits. */
>  #define SR_WIP                 1       /* Write in progress */
>  #define SR_WEL                 2       /* Write enable latch */
> @@ -67,6 +71,8 @@
>
>  #define SR_QUAD_EN_MX          0x40    /* Macronix Quad I/O */
>
> +#define EVCR_QUAD_EN_MICRON    0x80    /* Micron Quad I/O */
> +
>  /* Flag Status Register bits */
>  #define FSR_READY              0x80
>

thanks!
-- 
Jagan.
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