linux-kernel - Re: [RFC PATCH 0/3] Add new reg_update

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Message-ID: <CADBw62qEfdLM9e2oyPKz1qRk4mZaFPbXRYpLfVHzxKj0Cz90kw@mail.gmail.com>
Date:   Thu, 9 Apr 2020 17:40:08 +0800
From:   Baolin Wang <baolin.wang7@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Lee Jones <lee.jones@...aro.org>, Mark Brown <broonie@...nel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Lyra Zhang <zhang.lyra@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/3] Add new reg_update_bits() support

On Thu, Apr 9, 2020 at 5:15 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Thu, Apr 9, 2020 at 10:58 AM Baolin Wang <baolin.wang7@...il.com> wrote:
> >
> > The Spreadtrum platform uses a special set/clear method to update
> > registers' bits, thus this patch set introduces a new reg_update_bits()
> > callback, as well as adding a helper in syscon driver to support
> > this feature.
> >
> > Any comments are welcome. Thanks.
>
> This looks like a good idea to me, both the concept and the implementation.

Thanks for your quick response :)

>
> The one thing I'd note is that we have a similar mechanism for devices made
> by Sigmatel and later Freescale after they acquired them.
> include/linux/stmp_device.h only holds a couple of definitions, so it's much
> less abstract than your approach, but the idea is similar.

Ah, yes, sigmatel devices' idea is similar with ours.

>
> It would be nice in theory to move the sigmatel devices over to
> reg_update_bits() in theory, but this seems unlikely to actually happen,
> given that these are mostly obsolete drivers at this point.

I checked all sigmatel devices (about 10 drivers), I think there will
be more work to change them to use syscon/regmap when changing to
reg_update_bits(). I am afraid I can not thelp to convert them without
a hardware, and as you said, some drivers are already dead. So I think
it would be nice if the driver owners can help to convert these
drivers, if we get a consensus about the reg_update_bits()
implementation at last.

-- 
Baolin Wang