linux-kernel - Re: [PATCH v2 1/7] clk: Add a generic clock infrastructure

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Date:	Fri, 14 Oct 2011 11:14:19 -0700
From:	"Turquette, Mike" <mturquette@...com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-arm-kernel@...ts.infradead.org, jeremy.kerr@...onical.com,
	broonie@...nsource.wolfsonmicro.com, tglx@...utronix.de,
	linus.walleij@...ricsson.com, amit.kucheria@...aro.org,
	dsaxena@...aro.org, patches@...aro.org,
	linaro-dev@...ts.linaro.org, paul@...an.com,
	grant.likely@...retlab.ca, sboyd@...cinc.com,
	shawn.guo@...escale.com, skannan@...cinc.com,
	magnus.damm@...il.com, arnd.bergmann@...aro.org,
	linux@....linux.org.uk, eric.miao@...aro.org,
	richard.zhao@...aro.org, Mike Turquette <mturquette@...com>
Subject: Re: [PATCH v2 1/7] clk: Add a generic clock infrastructure

On Thu, Sep 22, 2011 at 3:26 PM, Mike Turquette <mturquette@...com> wrote:
> From: Jeremy Kerr <jeremy.kerr@...onical.com>
>  struct clk_hw_ops {
>        int             (*prepare)(struct clk_hw *);
>        void            (*unprepare)(struct clk_hw *);
>        int             (*enable)(struct clk_hw *);
>        void            (*disable)(struct clk_hw *);
>        unsigned long   (*recalc_rate)(struct clk_hw *);

In implementing recalc for divider clocks, I started to wonder, "why
not just pass struct clk *clk into the clk_hw_ops func ptrs?".

recalc is an obvious example whereby we need access to parent->rate.
The code usually ends up looking something like:

unsigned long omap_recalc_rate(struct clk_hw *hw)
{
        struct clk *parent;
        struct clk_hw_omap *oclk;

        parent = hw->clk->parent;
        oclk = to_clk_omap(hw);
        ...
}

That's a bit of a song and dance to have to do in almost every op, and
often these ops will need access to stuff like clk->rate also.   Is
there any opposition to just passing in struct clk?  e.g:

unsigned long omap_recalc_rate(struct clk *clk)
{
        struct clk *parent;
        struct clk_hw_omap *oclk;

        parent = clk->parent;
        oclk = to_clk_omap(clk->hw);
        ...
}

It is a small nitpick, but it affects the API for everybody so best to
get it right now before folks start migrating over to it.

Thanks,
Mike

>        int             (*set_rate)(struct clk_hw *,
>                                        unsigned long, unsigned long *);
>        long            (*round_rate)(struct clk_hw *, unsigned long);
>        int             (*set_parent)(struct clk_hw *, struct clk *);
>        struct clk *    (*get_parent)(struct clk_hw *);
>  };
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