linux-kernel - Re: [PATCH v5 2/2] mtd: spi-nor: macronix: Add support for mx66lm1g45g

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Date:   Mon, 20 Dec 2021 16:48:29 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     <Tudor.Ambarus@...rochip.com>
CC:     <michael@...le.cc>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Nicolas.Ferre@...rochip.com>
Subject: Re: [PATCH v5 2/2] mtd: spi-nor: macronix: Add support for
 mx66lm1g45g

On 20/12/21 11:10AM, Tudor.Ambarus@...rochip.com wrote:
> On 12/20/21 12:25 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Hi Tudor,
> > 
> > On 17/12/21 08:06PM, Tudor Ambarus wrote:
> >> mx66lm1g45g supports just 1-1-1, 8-8-8 and 8D-8D-8D modes. There are
> >> versions of mx66lm1g45g which do not support SFDP, thus use
> >> SPI_NOR_SKIP_SFDP. The RDID command issued through the octal peripheral
> >> interface outputs data always in STR mode for whatever reason. Since
> >> 8D-8D-8S is not common, avoid reading the ID when enabling the octal dtr
> >> mode. Instead, read back the CR2 to check if the switch was successful.
> > 
> > I replied to your v2 just now about this.
> > 
> >> Tested in 1-1-1 and 8d-8d-8d modes using sama7g5 QSPI IP.
> > 
> > Link to datasheet in the commit message would be nice.
> 
> Do you know if there's a standardized way to add a link to a datasheet
> in the commit message, i.e. should I use the Link tag or just a simple
> link will do?

I don't know if there is. Something like "Datasheet: <link>" should be 
fine I think.

> > 
> > As discussed on IRC, this flash reverses byte order in 8D-8D-8D mode. So
> > the data you write in 1S-1S-1S mode will be have byte order reversed
> > when reading in 8D-8D-8D mode. Do you have any plans on doing something
> > for this? Or do we just leave it to the user to figure it out?
> 
> I don't think we should amend this in software. Reading/writing in
> 8D-8D-8D will give sane results, the problem is just when you
> use STR for write and DTR for read, or viceversa. This is just a bad
> design and we should leave it as it is.

Sounds good to me.

> 
> I'll address all your other comments in a v6. Thanks.
> ta

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.