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

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Date:	Wed, 17 Dec 2014 15:31:25 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Arun Ramamurthy <arun.ramamurthy@...adcom.com>
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 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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