linux-kernel - Re: [RFC 17/17] clk: zynq: remove call to of_clk

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Date:	Sat, 24 Aug 2013 01:38:51 +0200
From:	Steffen Trumtrar <s.trumtrar@...gutronix.de>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>
Cc:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Michal Simek <michal.simek@...inx.com>,
	linux-kernel@...r.kernel.org,
	Mike Turquette <mturquette@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 17/17] clk: zynq: remove call to of_clk_init

On Fri, Aug 23, 2013 at 09:00:23AM -0700, Sören Brinkmann wrote:
> Hi Steffen,
> 
> On Fri, Aug 23, 2013 at 09:32:50AM +0200, Steffen Trumtrar wrote:
> > Hi!
> > 
> > On Thu, Aug 22, 2013 at 05:59:36PM -0700, Sören Brinkmann wrote:
> > > On Thu, Aug 22, 2013 at 05:26:47PM -0700, Sören Brinkmann wrote:
> [ ... ]
> > I propose getting rid of the whole global pointer and let the clkc map the
> > address itself instead.
> > 
> > Then there is no need to shuffle stuff around in the initcalls.
> > I have some WIP patches (not rebased on next and not even tested with it,
> > but with v3.11-rc4)
> > 
> > The dtsi would be something like:
> > 
> >        control-register@...00000 {
> > 	       compatible = "simple-bus";
> >                #address-cells = <1>;
> >                #size-cells = <1>;
> >                reg = <0xf8000000 0x1000>;
> >                ranges;
> > 
> >                slcr: slcr@...00000 {
> >                        compatible = "xlnx,zynq-slcr", "syscon";
> >                        reg = <0xf8000000 0x10>;
> >                };
> > 
> >                clkc: clkc@...00100 {
> >                        #clock-cells = <1>;
> >                        compatible = "xlnx,ps7-clkc";
> >                        reg = <0xf8000100 0x100>;
> 
> This is splitting the SLCR into multiple regions. I just heard about the
> syscon the first time, but wouldn't it be more correct to leave the SLCR
> region in one piece in the slcr node and then pass the slcr phandle to
> the clkc and later also pinmux etc. nodes? This way the SLCR is in
> charge of the lock and all registers protected by the lock.
> That wouldn't get rid of the dependency that SLCR has to be initialized
> before any of its users, but seems to reflect actual HW better since the
> whole region is protected by the same SLCR lock which makes them kinda
> inseparable.
> 

Actually I agree. What I was struggeling with, was the correct mapping of the
ranges. But maybe I have to take another look at the "ranges = <..>" property.

> Anyway, after all we more or less agree, that syscon/slcr has to be
> initialized before any SLCR user. So, no matter whether we do this
> through current code and a global pointer or DT phandles, the effect
> stays the same, IIUC.
> So, in order to not mix stuff around too much, I'd rather make sure that
> zynq_slcr_init() is called early enough (put it in init_irq() or some
> init_call() whatever works best), and keep the global pointer for now.
> That way most code can stay as is and we don't have to change the DT
> bindings.
> And then you can finish your work on this and we can revisit the topic
> of migrating to use the slcr through a phandle later?
> 

Agreed.

Steffen

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