linux-kernel - Re: [PATCH 1/6 v2] arm: use devicetree to get smp

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Date:	Mon, 05 Nov 2012 16:49:09 -0600
From:	Mark Langsdorf <mark.langsdorf@...xeda.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/6 v2] arm: use devicetree to get smp_twd clock

On 11/05/2012 04:31 PM, Russell King - ARM Linux wrote:
> On Mon, Nov 05, 2012 at 04:28:05PM -0600, Mark Langsdorf wrote:
>> On 11/04/2012 04:08 AM, Russell King - ARM Linux wrote:
>>> On Fri, Nov 02, 2012 at 01:51:44PM -0500, Mark Langsdorf wrote:
>>>> -static struct clk *twd_get_clock(void)
>>>> +static struct clk *twd_get_clock(struct device_node *np)
>>>>  {
>>>> -	struct clk *clk;
>>>> +	struct clk *clk = NULL;
>>>>  	int err;
>>>>  
>>>> -	clk = clk_get_sys("smp_twd", NULL);
>>>> +	if (np)
>>>> +		clk = of_clk_get(np, 0);
>>>> +	if (!clk)
>>>
>>> What does a NULL return from of_clk_get() mean?  Where is this defined?
>>
>> Well, it's a valid path if (np) is NULL. I'll add an IS_ERR(clk) and
>> resubmit.
> 
> Hang on - what logic are you trying to achieve here?  Wouldn't:
> 
> 	if (np)
> 		clk = of_clk_get(np, 0);
> 	else
> 		clk = clk_get_sys("smp_twd", NULL);
> 
> be sufficient?  If we have DT, why would we ever want to fall back to
> "smp_twd" ?

I'm just trying to make sure I have a clock so I can do cpufreq operations.

Your solution works and is sufficient. Thanks.

--Mark Langsdorf
Calxeda, Inc.


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