linux-kernel - Re: [GIT PULL] DT clk binding support

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Date:	Mon, 21 May 2012 21:17:17 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Shawn Guo <shawn.guo@...aro.org>
CC:	Rob Herring <robherring2@...il.com>,
	Mike Turquette <mturquette@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"arm@...nel.org" <arm@...nel.org>,
	Shawn Guo <shawn.guo@...escale.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Saravana Kannan <skannan@...eaurora.org>
Subject: Re: [GIT PULL] DT clk binding support

On 05/21/12 19:15, Shawn Guo wrote:
> On Mon, May 21, 2012 at 06:52:37PM -0500, Rob Herring wrote:
>> As Grant states: "This proposed binding is only about one thing:
>> attaching clock providers to clock consumers." This means you have to
>> have at least a single provider and a single consumer defined in the DT.
>>
> I just read through Grant's comments over again.  I agree with the
> statement which implicitly requires the clk provider defined in DT.
> However, for some case, this provider in DT is just a skeleton which
> is backed by clock driver where the provider is actually defined.
>
> Looking at Grant's comment below, the second option is also to match
> the clock in driver just using name.  The only difference to my
> proposal is the name here is given by the argument of phandle pointing
> to that skeleton provider node.
>
> I'm fine with that.  So go ahead with your bindings.
>

Can we do what the regulator framework has done and have a common
binding of <connection_name>-clk = <&phandle>? Something like:

    core-clk = <&uart3_clk>

and then have clk_get() use the of node of the device passed in to find
a property named %s-clk and find the clock with the matching phandle.

This looks like it's trying to cover both the end consumers (uart uses
uart3_clk) and the internal clock tree consumers (a crystal oscillator
connects to a PLL or a mux has multiple parents). We can certainly use
these bindings for muxes and internal parent-child relationships but I
would prefer we use different bindings for consumer bindings that match
what regulators do today.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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