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

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Message-ID: <213719a3-ed81-b1c6-9c9e-85dbeee85ff5@microchip.com>
Date:   Mon, 20 Dec 2021 11:10:12 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...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 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?
> 
> 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.

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