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

Boris Brezillon
2020-02-27T18:07:36Z

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

> From: Shivamurthy Shastri <sshivamurthy@micron.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@micron.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