linux-kernel - RE: [EXT] Re: [PATCH 3/4] mtd: spinand: Add M70A series Micron SPI NAND devices

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Message-ID: <DM6PR08MB63964244F066A3BC2220AD1EB80F0@DM6PR08MB6396.namprd08.prod.outlook.com>
Date:   Thu, 23 Jan 2020 09:01:50 +0000
From:   "Shivamurthy Shastri (sshivamurthy)" <sshivamurthy@...ron.com>
To:     'Miquel Raynal' <miquel.raynal@...tlin.com>
CC:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Shivamurthy Shastri <shiva.linuxworks@...il.com>
Subject: RE: [EXT] Re: [PATCH 3/4] mtd: spinand: Add M70A series Micron SPI
 NAND devices

Hi Miquel,

> 
> Hi Shivamurthy,
> 
> "Shivamurthy Shastri (sshivamurthy)" <sshivamurthy@...ron.com> wrote
> on
> Tue, 21 Jan 2020 14:59:11 +0000:
> 
> > Hi Miquel,
> >
> > >
> > > Hi Shivamurthy,
> > >
> > > "Shivamurthy Shastri (sshivamurthy)" <sshivamurthy@...ron.com>
> wrote
> > > on
> > > Tue, 21 Jan 2020 12:23:20 +0000:
> > >
> > > > Hi Miquel,
> > > >
> > > > >
> > > > > Hi Shiva,
> > > > >
> > > > > This is remark common to the four patches: you miss the 'v2' prefix in
> > > > > the object.
> > > > >
> > > >
> > > > Sorry for this mistake.
> > > > I recognized this after sending out the patches.
> > > >
> > > > > shiva.linuxworks@...il.com wrote on Sun, 19 Jan 2020 15:54:31
> +0100:
> > > > >
> > > > > > From: Shivamurthy Shastri <sshivamurthy@...ron.com>
> > > > > >
> > > > > > Add device table for M70A series Micron SPI NAND devices.
> > > > > >
> > > > > > While at it, disable the Continuous Read feature which is enabled by
> > > > > > default.
> > > > >
> > > > > Can you please give us more detail on why this is an issue?
> > > >
> > > > "Continuous Read" is the new feature added by the Micron for
> > > > M70A series devices. If this feature is enabled, the READ command
> > > > doesn't output the OOB area. The following short description
> > > > describes this feature.
> > > >
> > > > Description:
> > > > If the Continuous Read feature is enabled, the device provides
> > > > the capability to read the whole block with a single command.
> > > > However, the read command doesn't output the OOB area.
> > > >
> > > > Read command behavior (if Continuous Read enabled):
> > > > 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.
> > >
> > > Ok I understand better. In this case there is no need to split this
> > > commit, instead just reword the commit log to something like:
> > >
> > > --->8---
> > > Add device table for M70A series Micron SPI-NAND devices.
> > >
> > > As opposed to the M60A series already supported, M70A parts have the
> > > "Continuous Read" feature enabled by default which does not fit the
> > > subsystem needs.
> > >
> > > <here explain the feature>.
> > >
> > > Hence, we disable the feature at probe time.
> > > ---8<---
> > >
> >
> > Sure, I will change as per your suggestion.
> >
> > > However, below, you disable this bit for all the parts. Is this really
> > > ok? Souldn't we make it more specific to this series?
> >
> > It is ok because this bit is unused in other series.
> 
> I would rather prefer to avoid this kind of arrangement. Please change
> this bit only for the series which has it.

There is no other way to identify the series of the device except by using the
"flags" from the structure spinand_info. So I will proceed with this approach.

1. In spinand.h --> I will create macro

#define SPINAND_HAS_CR_FEAT_BIT         BIT(1)

2. Use this flag inside micron_spinand_init function to identify the device.


> 
> 
> Thanks,
> Miquèl

Thanks,
Shiva