linux-kernel - Re: [PATCH v5 4/4] clk: basic clock hardware types

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Date:	Fri, 9 Mar 2012 15:38:39 -0800
From:	"Turquette, Mike" <mturquette@...com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Sascha Hauer <s.hauer@...gutronix.de>,
	Russell King <linux@....linux.org.uk>, patches@...aro.org,
	linaro-dev@...ts.linaro.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnd Bergman <arnd.bergmann@...aro.org>,
	Paul Walmsley <paul@...an.com>,
	Shawn Guo <shawn.guo@...escale.com>,
	Jamie Iles <jamie@...ieiles.com>,
	Richard Zhao <richard.zhao@...aro.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Deepak Saxena <dsaxena@...aro.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH v5 4/4] clk: basic clock hardware types

On Mon, Mar 5, 2012 at 2:17 AM, Andrew Lunn <andrew@...n.ch> wrote:
>> > I think i can wrap your simple gate clock, to make my "complex" gate
>> > clock. What would help is if you would EXPORT_SYMBOL_GPL
>> > clk_gate_enable() and clk_gate_disable(), since they do exactly what i
>> > want. I can then build my own clk_ops structure, with my own
>> > unprepare() function. I would probably use DEFINE_CLK_GATE as is, and
>> > then at run time, before calling __clk_init() overwrite the .ops with
>> > my own version.
>>
>> Maybe I don't get your point, but clk_unprepare should be used when
>> you have to sleep to disable your clock. When clk_gate_disable() is
>> exactly why do you want to use clk_unprepare instead of clk_disable?
>
> I'm trying to avoid having to implement a new clock provider. The
> whole point of the generic clk code is to consolidate code. It seems
> silly to create a new clk provider which is 95% identical to Mike's
> gated provider, if i can avoid it.

I will export the operations in my next patchset, but I'm concerned
over how useful this might be...

Using your example of struct clk_gate, both clk_gate_enable and
clk_gate_disable call to_clk_gate.  So you would either have to re-use
struct clk_gate for your own needs (which involves hacking up a
specific struct clk_gate_foo_ops for your needs) or you could not use
struct clk_gate and pack your data identically (struct clk_hw must be
the first member) which is too horrible to imagine.

Hmm, or you could re-use struct clk_gate but provide your own struct
clk_ops AND your own registration functions (since you won't be able
to pass in the ops to your clk_register_gate).  So that sounds sane,
if a bit convoluted.  It does re-use code though...

Regards,
Mike

>
> If i stuff it into clk_disable(), it means i cannot use the basic gate
> clock Mike provides in the generic clock framework. Which is a shame,
> since it does exactly what i want in terms of gating the clock.
>
> If i can use unprepare(), which basic gate does not use, i can use
> Mikes code, and just extend it. It is there, it is unused, so why not
> use it?
>
>    Andrew
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