linux-kernel - Re: [PATCH V2] clk: Add composite clock type

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Message-id: <1554530.H35cUWvpSY@amdc1227>
Date:	Tue, 05 Feb 2013 11:38:46 +0100
From:	Tomasz Figa <t.figa@...sung.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Hiroshi Doyu <hdoyu@...dia.com>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	"mturquette@...aro.org" <mturquette@...aro.org>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"sboyd@...eaurora.org" <sboyd@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH V2] clk: Add composite clock type

On Tuesday 05 of February 2013 11:22:52 Hiroshi Doyu wrote:
> Prashant Gaikwad <pgaikwad@...dia.com> wrote @ Tue, 5 Feb 2013 09:33:41 
+0100:
> > > The members of "clk_composite_ops" seems to be always assigned
> > > statically. Istead of dynamically allocating/assigning, can't we
> > > just
> > > have "clk_composite_ops" statically as below?
> > > 
> > > static struct clk_ops clk_composite_ops = {
> > > 
> > > 	.get_parent = clk_composite_get_parent;
> > > 	.set_parent = clk_composite_set_parent;
> > > 	.recalc_rate = clk_composite_recalc_rate;
> > > 	.round_rate = clk_composite_round_rate;
> > > 	.set_rate = clk_composite_set_rate;
> > > 	.is_enabled = clk_composite_is_enabled;
> > > 	.enable = clk_composite_enable;
> > > 	.disable = clk_composite_disable;
> > > 
> > > };
> > > 
> > > struct clk *clk_register_composite(struct device *dev, const char
> > > *name,> > 
> > > 		       const char **parent_names, int num_parents,
> > > 		       struct clk_hw *mux_hw, const struct clk_ops 
*mux_ops,
> > > 		       struct clk_hw *div_hw, const struct clk_ops 
*div_ops,
> > > 		       struct clk_hw *gate_hw, const struct clk_ops 
*gate_ops,
> > > 		       unsigned long flags)
> > > 
> > > {
> > > 
> > > 	.....
> > > 	
> > > 	init.ops = &clk_composite_ops;
> > 
> > No, clk_ops depends on the clocks you are using. There could be a
> > clock
> > with mux and gate while another one with mux and div.
> 
> You are right. What about the following? We don't have to have similar
> copy of clk_composite_ops for each instances.
> 
> diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
> index f30fb4b..8f88805 100644
> --- a/drivers/clk/clk-composite.c
> +++ b/drivers/clk/clk-composite.c
> @@ -27,6 +27,9 @@ static u8 clk_composite_get_parent(struct clk_hw *hw)
>         const struct clk_ops *mux_ops = composite->mux_ops;
>         struct clk_hw *mux_hw = composite->mux_hw;
> 
> +       if (!mux_hw->clk)
> +	       return -EINVAL;
> +

Or maybe even:

		if (!mux_ops)

This would be more self-explanatory and save one dereference.

Best regards,
-- 
Tomasz Figa
Samsung Poland R&D Center
SW Solution Development, Linux Platform

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