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

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Date:   Thu, 27 Feb 2020 20:34:20 +0000
From:   "Shivamurthy Shastri (sshivamurthy)" <sshivamurthy@...ron.com>
To:     Boris Brezillon <boris.brezillon@...labora.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-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shiva.linuxworks@...il.com" <shiva.linuxworks@...il.com>
Subject: RE: [EXT] Re: [PATCH v4 3/5] mtd: spinand: micron: identify SPI NAND
 device with Continuous Read mode

Hi Boris,

Thanks for the review.

> 
> 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?

I will change the name.
Yes, only Micron uses this BIT for Continuous Read feature.

> 
> > +
> >  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)

Okay.

> 
> > +		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