linux-kernel - Re: [PATCH] mtd: spi-nor: honour max_data

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Message-ID: <87sh5riqxx.fsf@notabene.neil.brown.name>
Date:   Wed, 13 Jun 2018 08:24:26 +1000
From:   NeilBrown <neil@...wn.name>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     Yogesh Gaur <yogeshnarayan.gaur@....com>,
        linux-mtd@...ts.infradead.org, boris.brezillon@...e-electrons.com,
        frieder.schrempf@...eet.de, computersforpeace@...il.com,
        david.wolfe@....com, han.xu@....com, festevam@...il.com,
        marek.vasut@...il.com, prabhakar.kushwaha@....com,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: honour max_data_size for spi-nor writes

On Tue, Jun 12 2018, Boris Brezillon wrote:

>
> Just because you managed to solve the problem in one driver does not
> mean the problem does not exist for others. I read this datasheet [1]
> several times and couldn't find a way to say 'I want to keep the CS
> asserted between 2 transactions', so I think we really need this patch.

I agree that my experience doesn't necessarily generalize.  As the patch
carried by signed-off-by (even though I only wrote little parts of it) I
wanted to make it clear that I had no desire to promote the patch -
maybe I stated that too strongly.

Thanks for the link to the data sheet.  I had a bit of a look, but
reading these things must be an art that I haven't fully mastered yet -
it would probably take me a few days to really understand it.
The Programmable Sequence Enginine (Section 10.2.5.3.1) seems
interesting. I wouldn't be surprised that that lets you do interesting
things.

It is obviously quite a powerful unit and it is surprising - to me -
that it might not allow arbitrarily long messages, but I cannot justify
the time to really dig in and see if that is the case.
Maybe you are right.  I have no particular objections to the patch, I
just don't want to be seen as speaking in favour of it.

Thanks,
NeilBrown

>
> Regards,
>
> Boris
>
> [1]https://www.nxp.com/docs/en/reference-manual/VFXXXRM.pdf

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