linux-kernel - Re: [PATCH] mtd: spi-nor: stop printing superfluous debug info

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Message-ID: <20231128120424.79f8f215@xps-13>
Date:   Tue, 28 Nov 2023 12:04:24 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Tudor Ambarus <tudor.ambarus@...aro.org>
Cc:     liao jaime <jaimeliao.tw@...il.com>,
        Michael Walle <michael@...le.cc>, jaimeliao@...c.com.tw,
        pratyush@...nel.org, richard@....at, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: stop printing superfluous debug info

Hello,

tudor.ambarus@...aro.org wrote on Tue, 28 Nov 2023 09:47:22 +0000:

> On 11/28/23 09:39, Tudor Ambarus wrote:
> > 
> > cut
> >   
> >>>> Maybe we don't need this at all, as long as one message remains about
> >>>> the JEDEC ID, but keep in mind that spi-nors are commonly storing the
> >>>> rootfs and if your spi-nor does not boot you don't have a userspace yet
> >>>> and all the debugfs entries are purely useless.  
> >>>
> >>> Good point.
> >>>
> >>> Just curious, do you know any boards which has the rootfs writable on
> >>> the spi-nor flash?  
> >> I am also interested.
> >>  
> > 
> > Having the rootfs stored on SPI NOR is a poor design decision as you're
> > better of with a NAND, which is cheaper and faster on writes. I tried in
> > the past a ubifs on top of a large (64 and 128MB) SPI NOR flash. But
> > they were plug-able flashes, not something that is always tied to the
> > board. Microchip's sama7g5ek comes with a 128MB macronix SPI NOR flash
> > populated. But there are other vendors that provide large SPI NORs if
> > really needed.
> >   
> 
> pressed sent too soon :). What I wanted to say is that it's not uncommon
> for vendors to populate large SPI NOR flashes, there are others as well,
> thus Miquel's concerns are valid. There may be people out there having
> rootfs on top of SPI NORs.

I don't think it is a too bad approach to store a rootfs on a spi-nor,
as long as your "regularly written" data files are somewhere else
(otherwise it's fine, but slow). It's actually nice to keep your boot
files and rootfs in a "safe" place whereas your app is stored somewhere
else, so users can mess around: they will not break the system.

Thanks,
Miquèl