linux-kernel - Re: [PATCH 1/8] sta2x11-mfd : add apb-soc regs driver and factor out common code

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Date:	Wed, 26 Sep 2012 18:31:45 +0200
From:	Davide Ciminaghi <ciminaghi@...dd.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	sameo@...ux.intel.com, rubini@...dd.com, giancarlo.asnaghi@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] sta2x11-mfd : add apb-soc regs driver and factor out common code

On Wed, Sep 26, 2012 at 04:04:29PM +0100, Mark Brown wrote:
> On Wed, Sep 26, 2012 at 04:56:15PM +0200, Davide Ciminaghi wrote:
> > On Tue, Sep 25, 2012 at 08:20:48PM +0100, Mark Brown wrote:
> 
> > > Glancing at the diff here this looks a lot like regmap-mmio...  not sure
> > > if it is or not, though.
> 
> > that would be ideal, but I also need to deal with the common clock framework,
> > which doesn't support regmap: clk_register_divider(), clk_register_mux(),
> > clk_register_gate(), all take a void __iomem * to access clock control
> > registers, so as far as I can understand we can't use regmap, unless of
> > course we convert the common clock framework to regmap.
> 
> The two should be able to coexist happily, regmap-mmio requires the
> caller to do the actual mapping and so long as you don't cache the
> relevant registers the two shouldn't interfere with each other.
>
Well, it just sounded not so clean to me having two ways for accessing the
same registers. The caller would be sta2x11-mfd in our case, while clock
registers are used by the common clock framework, so sta2x11-mfd should still
need to export some void __iomem *  to make the clock framework happy, while
other potential users could go via regmap.
Oh, and there's another problem (I'm looking at the code right now, I had
forgotten about this): the clock framework also asks for a spinlock_t *.
Regmap has its own spinlock (or mutex), and I don't think it would be a
good idea trying to export it.
So, as far as I can understand at present, the best thing to do would be
adding regmap support to the clock framework, which wouldn't be trivial
because I guess we should keep compatibility with the present
clk_register_... api

Davide
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