Re: [PATCHv1] rtc: bcm-iproc: Add support for Broadcom iproc rtc

[Arun Ramamurthy]

On 15-03-04 02:58 PM, Arnd Bergmann wrote:
> On Wednesday 04 March 2015 14:53:40 Arun Ramamurthy wrote:
> > On 15-03-04 02:50 PM, Arnd Bergmann wrote:
> > > On Wednesday 04 March 2015 14:40:13 Arun Ramamurthy wrote:
> > > > On 15-03-04 02:21 PM, Arnd Bergmann wrote:
> > > > > On Thursday 12 February 2015 14:17:41 Arun Ramamurthy wrote:
> > > > > > Hi Arnd
> > > > > >
> > > > > > My apologies for the late reply, I was moved to other work items. I
> > > > > > wanted to get more clarification on the syscon issue so that I can
> > > > > > submit the next patch set. If I understand correctly, you would like
> > > > > > me to move the CRMU logic to a new driver under mfd/ and use the syscon
> > > > > > api calls in my rtc driver? Thanks
> > > > >
> > > > > It depends a lot on what's in there, I can best advise you if you
> > > > > have some form of register list.
> > > > >
> > > > > A common approach would be to not have a driver for the crmu at all,
> > > > > but just mark it as syscon, and have the other drivers either reference
> > > > > the syscon node through a phandle, or create them as childrem of
> > > > > the syscon node. The latter case makes most sense if all uses of
> > > > > the crmu have no other MMIO registers.
> > > >
> > > > Thank you Arnd, I am going to follow the approach of adding a child node
> > > > to the syscon node. Several other driver use other registers in the CRMU
> > > > so I think the child node approach makes the most sense.
> > >
> > > Just to be sure we have the same understanding: of those other drivers,
> > > do you think that they would use only CRMU registers, or could there
> > > be drivers that have both CRMU as well as other MMIO registers?
> > The other drivers have both CRMU and other MMIO registers. So I thought
> > they could also switch to using the syscon child nodes.
>
> No, in this case, better not use child nodes at all. When other platforms
> use child nodes of a syscon, the common case is that they use the 'reg'
> property to refer to syscon registers, which are in a different address
> space from other MMIO, and you can't easily mix the two.

Arnd, this is the device tree entry that I would end up with and I plan 
to use syscon_regmap_lookup_by_phandle in the rtc driver. Does this look 
acceptable?

rtc: iproc_rtc@0x03026000 {
		compatible = "brcm,iproc-rtc";
		reg =	<0x03026000 0xC>,
		iso_cell_syscon = <&crmu_iso_cell_control>;
		bbl_auth_syscon = <&crmu_bbl_auth>
		status = "okay";

crmu_iso_cell_control:crmu@0x0301C02C {
		compatible = "syscon";
		reg = <0x0301C038 0x8>
}

crmu_bbl_auth:crmu@0x03024C74 {
		compatible = "syscon";
		reg = <0x03024C74 0x8>;
}

Thanks
> 	Arnd
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