linux-kernel - Re: [RFC PATCH] clk: add extension API

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Date:	Thu, 31 May 2012 14:12:20 -0700
From:	Saravana Kannan <skannan@...eaurora.org>
To:	Peter De Schrijver <pdeschrijver@...dia.com>
CC:	Mike Turquette <mturquette@...com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH] clk: add extension API

On 05/31/2012 01:23 AM, Peter De Schrijver wrote:
> On Thu, May 31, 2012 at 05:29:54AM +0200, Saravana Kannan wrote:
>> On 05/30/2012 12:40 PM, Mike Turquette wrote:
>>> On 20120530-01:52, Stephen Boyd wrote:
>>>> On 5/29/2012 2:58 AM, Peter De Schrijver wrote:
>>>>> Add an extension API for clocks. This allows clocktypes to provide extensions
>>>>> for features which are uncommon and cannot be easily mapped onto normal clock
>>>>> framework concecpts. eg: resetting blocks, configuring clock phase etc.
>>>>
>>>> This seems rather generic. Why not add more specific APIs/concepts like
>>>> clk_reset(), clk_set_phase(), etc.? If they don't map, maybe we should
>>>> make them map.
>>>>
>>>
>>> I also wonder if exposing some of these knobs should be done in the
>>> basic clock types.  Meaning that instead of having additional calls in
>>> the clk.h API those calls could be exposed by the basic clock types that
>>> map to the actions.
>>>
>>> The question that needs to be answered is this: do generic drivers need
>>> access to these additional functions (clk.h) or just the platform code
>>> which implements some of the clock logic (basic clock types&
>>> platform-speciic clock types).
>>
>> One of the main reason for the common clock framework is so that each
>> platform doesn't have it's own extension and have mostly similar code
>> repeat all over the place. So, having clock APIs outside of clk.h
>> doesn't make sense when we look at the direction we want the code base
>> to proceed in.
>
> I don't think this will lead to 'mostly similar code repeat all over the
> place'. I don't know of any intree SoC which has a similar requirement.
> So which code duplication would this cause?

It's not clear what you plan to use this API for. So, I can't really 
answer if any intree SoC needs it. But if this is about reset signals, 
it's definitely needed for MSM too. I was planning on bringing this up 
after the basic clock API implementation in the clock framework is 
usable for MSM.

-Saravana

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