linux-kernel - Re: [PATCH v2] clkdev: add devm_of_clk

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Date:	Thu, 07 Jul 2016 18:30:09 -0700
From:	Michael Turquette <mturquette@...libre.com>
To:	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	"Russell King - ARM Linux" <linux@...linux.org.uk>
Cc:	"Rob Herring" <robh@...nel.org>, "Mark Brown" <broonie@...nel.org>,
	"Linux-Kernel" <linux-kernel@...r.kernel.org>,
	"Linux-DT" <devicetree@...r.kernel.org>,
	"Linux-ARM" <linux-arm-kernel@...ts.infradead.org>,
	"Linux-ALSA" <alsa-devel@...a-project.org>,
	linux-clk@...r.kernel.org
Subject: Re: [PATCH v2] clkdev: add devm_of_clk_get()

Quoting Kuninori Morimoto (2016-07-07 17:03:00)
> 
> Hi Russell
> 
> > > > > +struct clk *devm_of_clk_get(struct device *dev,
> > > > > +                           struct device_node *np, int index)
> > > > 
> > > > Any reason not to use devm_clk_get? Why do we need this helper?
> > > 
> > > Because of_clk_get() can parse "clocks", "#clock-cells" on DT.
> > 
> > clk_get() should also work just fine.  clk_get() uses
> > __of_clk_get_by_name() internally, which uses "clock-names" to
> > locate the index if a connection id is given.  of_clk_get() allows
> > lookup of a clock by index only, omitting the name, which means
> > you need to coordinate the order of clocks in DT with the order
> > that the driver wants... which sounds error prone to me.
> 
> Thanks.
> 
> But, I have 1 issue on [devm_]clk_get().
> It can't select device_node on [devm_]clk_get(), it uses dev->of_node directly.
> 
> struct clk *clk_get(struct device *dev, const char *con_id)
> {
>         ...
>         if (dev) {
>                 clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
>                                            ~~~~~~~~~~~~
>                 ...
>         }
> }
> 
> I would like to select specific device_node.

Do you have access to the struct device that you want to target? Can you
pass that device into either clk_get or devm_clk_get?

Regards,
Mike

> 
>         sound_soc {
>                 ...
>                 cpu {
>                         ...
> =>                      clocks = <&xxx>;
>                 };
> 
>                 codec {
>                         ...
> =>                      clocks = <&xxx>;
>                 };
>         };
> 
> But, of_clk_get_by_name() / of_clk_get() doesn't have devm_xxx version