linux-kernel - Re: [PATCH] tty: max310x: work around regmap->regcache data corruption

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Message-ID: <f6e93e9c-1c7a-424e-afe0-425b24b99e5c@sirena.org.uk>
Date:   Mon, 4 Dec 2023 19:48:05 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     Jan Kundrát <jan.kundrat@...net.cz>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        linux-serial@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: max310x: work around regmap->regcache data
 corruption

On Mon, Dec 04, 2023 at 02:41:36PM -0500, Hugo Villeneuve wrote:

> But that is not was my question was about. Here a pseudo code
> example to select "page" 1:

> 1. save original value of LCR register.
> 2. write 0xBF to LCR register
> 3. access desired register in page 1
> 4. restore original LCR value saved in step 1

> How do you do that with regmap range?

Are you saying that the selector has other, non-selector functions?
This is truly innovative hardware, generally the selector is just a
bitfield that you write paging values to.  You'd need to extend the core
so that it knows about this quirk, right now that's not possible and
we'll just leave the window pointing at whatever was last accessed.

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