linux-kernel - Re: [PATCH v4 3/5] mtd: spinand: micron: identify SPI NAND device with Continuous Read mode

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Message-ID: <20200227190729.1c5e4fef@collabora.com>
Date:   Thu, 27 Feb 2020 19:07:29 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     shiva.linuxworks@...il.com
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Shivamurthy Shastri <sshivamurthy@...ron.com>
Subject: Re: [PATCH v4 3/5] mtd: spinand: micron: identify SPI NAND device
 with Continuous Read mode

On Thu,  6 Feb 2020 21:22:04 +0100
shiva.linuxworks@...il.com wrote:

> From: Shivamurthy Shastri <sshivamurthy@...ron.com>
> 
> Add SPINAND_HAS_CR_FEAT_BIT flag to identify the SPI NAND device with
> the Continuous Read mode.
> 
> Some of the Micron SPI NAND devices have the "Continuous Read" feature
> enabled by default, which does not fit the subsystem needs.
> 
> In this mode, the READ CACHE command doesn't require the starting column
> address. The device always output the data starting from the first
> column of the cache register, and once the end of the cache register
> reached, the data output continues through the next page. With the
> continuous read mode, it is possible to read out the entire block using
> a single READ command, and once the end of the block reached, the output
> pins become High-Z state. However, during this mode the read command
> doesn't output the OOB area.
> 
> Hence, we disable the feature at probe time.
> 
> Signed-off-by: Shivamurthy Shastri <sshivamurthy@...ron.com>
> ---
>  drivers/mtd/nand/spi/micron.c | 16 ++++++++++++++++
>  include/linux/mtd/spinand.h   |  1 +
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/mtd/nand/spi/micron.c b/drivers/mtd/nand/spi/micron.c
> index 5fd1f921ef12..a8e947609cd9 100644
> --- a/drivers/mtd/nand/spi/micron.c
> +++ b/drivers/mtd/nand/spi/micron.c
> @@ -18,6 +18,8 @@
>  #define MICRON_STATUS_ECC_4TO6_BITFLIPS	(3 << 4)
>  #define MICRON_STATUS_ECC_7TO8_BITFLIPS	(5 << 4)
>  
> +#define MICRON_CFG_CONTI_READ		BIT(0)

Let's try to use consistent names. The feature bit is
SPINAND_HAS_CR_FEAT_BIT, so maybe MICRON_CFG_CR. BTW, is this really a
micron-specific bit?

> +
>  static SPINAND_OP_VARIANTS(read_cache_variants,
>  		SPINAND_PAGE_READ_FROM_CACHE_QUADIO_OP(0, 2, NULL, 0),
>  		SPINAND_PAGE_READ_FROM_CACHE_X4_OP(0, 1, NULL, 0),
> @@ -153,8 +155,22 @@ static int micron_spinand_detect(struct spinand_device *spinand)
>  	return 1;
>  }
>  
> +static int micron_spinand_init(struct spinand_device *spinand)
> +{
> +	/*
> +	 * M70A device series enable Continuous Read feature at Power-up,
> +	 * which is not supported. Disable this bit to avoid any possible
> +	 * failure.
> +	 */
> +	if (spinand->flags == SPINAND_HAS_CR_FEAT_BIT)

	if (spinand->flags & SPINAND_HAS_CR_FEAT_BIT)

> +		return spinand_upd_cfg(spinand, MICRON_CFG_CONTI_READ, 0);
> +
> +	return 0;
> +}
> +
>  static const struct spinand_manufacturer_ops micron_spinand_manuf_ops = {
>  	.detect = micron_spinand_detect,
> +	.init = micron_spinand_init,
>  };
>  
>  const struct spinand_manufacturer micron_spinand_manufacturer = {
> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
> index 4ea558bd3c46..333149b2855f 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -270,6 +270,7 @@ struct spinand_ecc_info {
>  };
>  
>  #define SPINAND_HAS_QE_BIT		BIT(0)
> +#define SPINAND_HAS_CR_FEAT_BIT		BIT(1)
>  
>  /**
>   * struct spinand_info - Structure used to describe SPI NAND chips