linux-kernel - Re: [RFC PATCH 2/3] regmap: Add reg_update

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Message-ID: <CADBw62oP-bJcjWaQiW1zAdix3c4=nfTkNTZZOti6bVtLJwp7+w@mail.gmail.com>
Date:   Fri, 10 Apr 2020 10:55:16 +0800
From:   Baolin Wang <baolin.wang7@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Lee Jones <lee.jones@...aro.org>, Arnd Bergmann <arnd@...db.de>,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/3] regmap: Add reg_update_bits() support

On Thu, Apr 9, 2020 at 10:26 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Thu, Apr 09, 2020 at 10:12:44PM +0800, Baolin Wang wrote:
> > On Thu, Apr 9, 2020 at 6:45 PM Mark Brown <broonie@...nel.org> wrote:
>
> > > MMIO devices clearly don't physically have an update_bits() operation so
> > > this should be implemented further up the stack where it applies to all
> > > buses without physical support.
>
> > I understood your concern. But the syscon driver need use the MMIO
> > devices' resources (such as address mapping, clock management and so
> > on), if move this to further up stack, I am afraid the update_bits()
> > can not use the resources in 'struct regmap_mmio_context'. Do you have
> > any good suggestion? Thanks.
>
> If the syscon driver needs to be peering into the regmap implementation
> that seems like there's a serious abstraction problem - users of the
> regmap shouldn't be looking at the implmentation at all.  Why do you
> think this is needed?

Sorry for confusing, that's not what I mean. My point is the syscon
driver will call the regmap_init_mmio() to use the MMIO regmap_bus,
but as you said, MMIO bus should not a physical bus, so I suppose the
syscon driver should create a new phycical regmap bus for our special
case, but the problem is the phycical regmap bus implementation will
be similar with the MMIO bus except adding a reg_update_bits()
callback, which will introduce more duplicated code. What do you
think？

-- 
Baolin Wang