linux-kernel - Re: [Patch v3] driver/clk/clk-si5338: Add common clock framework driver for si5338

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Date:	Wed, 17 Jun 2015 10:18:25 -0700
From:	York Sun <yorksun@...escale.com>
To:	Paul Bolle <pebolle@...cali.nl>
CC:	<mturquette@...libre.com>, <linux-kernel@...r.kernel.org>,
	<linux-i2c@...r.kernel.org>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Andrey Filippov <andrey@...hel.com>
Subject: Re: [Patch v3] driver/clk/clk-si5338: Add common clock framework
 driver for si5338



On 06/17/2015 02:29 AM, Paul Bolle wrote:
> On Tue, 2015-06-16 at 09:31 -0700, York Sun wrote:
>> COMMON_CLK in Kconfig is changed from bool to tristate so all common
>> clock framework drivers can be selected by users.
> 
> A bool to tristate change isn't needed to make it possible to set a
> symbol manually. That's achieved by adding a prompt (which the patch
> also does).
> 
> This change adds a prompt to the symbol that enables the framework. But,
> as far as I can see, clock drivers depending on that framework already
> can be set manually. So that's another reason the above looks incorrect
> to me.
> 
> Note that the "help" of COMMON_CLK contains:
>     Architectures utilizing the common struct clk should select
>     this option.
> 
> Does the architecture this patch targets perhaps not select COMMON_CLK?
> If that's the case, it seems you should change that architecture
> instead.

Paul,

I did check the mechanism to select COMMON_CLK. It doesn't fit my application.
But it is not in the scope of this patch. I will discuss at the end of this email.

> 
>> --- a/drivers/clk/Kconfig
>> +++ b/drivers/clk/Kconfig
> 
>>  config COMMON_CLK
>> -	bool
>> +	tristate "Common Clock"
>>  	select HAVE_CLK_PREPARE
>>  	select CLKDEV_LOOKUP
>>  	select SRCU
> 
> I told you yesterday that setting this to tristate allows over a dozen
> new modules to be created. I'd be surprised if that doesn't break stuff
> left and right without additional changes (which this patch lacks).

Yes you did. I checked over and over and believe enabling this option doesn't
break anything. By enabling it, a dozen modules are built either in the kernel,
or as modules (depending on y or m). They support fix-rate clock and others.

Here is what I am going to do. I will separate the Kconfig from this patch so it
doesn't block this patch from going forward. I will continue exploring the
correct way to enable common clock framework, for my application and for general
use.

York
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