Message-ID: <54F789CD.5030504@broadcom.com>
Date:	Wed, 4 Mar 2015 14:40:13 -0800
From:	Arun Ramamurthy <arun.ramamurthy@...adcom.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Ray Jui <rjui@...adcom.com>,
	<linux-arm-kernel@...ts.infradead.org>, <mark.rutland@....com>,
	<a.zummo@...ertech.it>, <sbranden@...adcom.com>,
	<pawel.moll@....com>, <devicetree@...r.kernel.org>,
	<ijc+devicetree@...lion.org.uk>,
	Arun Ramamurthy <arunrama@...adcom.com>,
	<linux-kernel@...r.kernel.org>, <grant.likely@...aro.org>,
	<robh+dt@...nel.org>, <bcm-kernel-feedback-list@...adcom.com>,
	<galak@...eaurora.org>, <rtc-linux@...glegroups.com>
Subject: Re: [PATCHv1] rtc: bcm-iproc: Add support for Broadcom iproc rtc



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.
>
>> On 14-12-17 06:31 AM, Arnd Bergmann wrote:
>>> On Tuesday 16 December 2014 13:54:04 Arun Ramamurthy wrote:
>>>> On 14-12-16 12:27 PM, Ray Jui wrote:
>>>>> On 12/16/2014 12:19 PM, Arnd Bergmann wrote:
>>>>>>
>>>>>> It sounds like CRMU is some other unit aside from the RTC. Could this
>>>>>> be something like a generic system controller? I think it should
>>>>>> either have its own driver or use the syscon logic if that is what
>>>>>> this is.
>>>>>>
>>>>> Giving that CRMU has scattered, miscellaneous control logic for multiple
>>>>> different peripherals, it probably makes more sense to use the syscon
>>>>> logic here.
>>>>>
>>>> Arnd, thanks for the feedback. If I was to write a separate driver for
>>>> the CRMU, I would have to export certain functions and create an api
>>>> that only this RTC driver would use. I am not sure that is efficient or
>>>> required. What is your opinion?
>>>> Would it be better if I use the syson api in my current driver and move
>>>> the CRMU registers to separate syscon device tree entry?
>>>>
>>>
>>> This is something that's normally up to the platform maintainers, depending
>>> on what works best for a given SoC. If you have a control block that
>>> wants to export the same high-level API for multiple drivers, that's
>>> fine, but if literally every register does something different, a syscon
>>> driver works best.
>>>
>>> It's also possible that some of the functions of the CRMU already have
>>> abstractions, like system-reset, device-reset, regulator or clock support.
>>> In that case, you can still use syscon but have the more other drivers
>>> use that for accessing the registers.
>>>
>>> 	Arnd
>>>
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