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

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Date:   Wed, 23 Nov 2016 11:10:37 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Mark Brown <broonie@...nel.org>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        Linux-DT <devicetree@...r.kernel.org>,
        Linux-Kernel <linux-kernel@...r.kernel.org>,
        linux-clk@...r.kernel.org,
        Linux-ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [alsa-devel] [PATCH v2] clkdev: add devm_of_clk_get()

On 11/16, Kuninori Morimoto wrote:
> 
> Hi Rob, Michael, Russell
> 
> 
> What is the conclusion of this patch ?
> We shouldn't add devm_of_clk_get() ? or can I continue ?
> 
> The problem of current [devm_]clk_get() handles *dev only,
> but I need to get clocks from DT node, not dev
> 
> 	sound_soc {
> 		...
> 		cpu {
> 			...
> =>			clocks = <&xxx>;
> 		};
> 		codec {
> 			...
> =>			clocks = <&xxx>;
> 		};
> 	};
> 

I've seen bindings that have the 'clocks' property at the top
level and the appropriate 'clock-names' property to relate the
clocks to a subnode.

 	sound_soc {
		clocks = <&xxx>, <&xxx>;
		clock-names = "cpu", "codec";
 		...
 		cpu {
 			...
 		};
 		codec {
 			...
 		};
 	};

Then the subnodes call clk_get() with the top level device and
the name of their node and things match up. I suppose this
binding is finalized though, so we can't really do that?

I see that the gpio framework has a similar design called
devm_get_gpiod_from_child(), so how about we add a
devm_get_clk_from_child() API? That would more closely match the
intent here, which is to restrict the clk_get() operation to
child nodes of the device passed as the first argument.

struct clk *devm_get_clk_from_child(struct device *dev,
				    const char *con_id,
				    struct device_node *child);

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