linux-kernel - Re: [PATCH 2/2] cpufreq: cpu0: Extend support beyond CPU0

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Date:	Tue, 1 Jul 2014 16:44:04 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Rob Herring <rob.herring@...aro.org>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Shawn Guo <shawn.guo@...aro.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arvind Chauhan <arvind.chauhan@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-arm-msm@...r.kernel.org, Sachin Kamat <spk.linux@...il.com>,
	Thomas P Abraham <thomas.ab@...sung.com>,
	Nishanth Menon <nm@...com>, Tomasz Figa <t.figa@...sung.com>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <Mark.Rutland@....com>
Subject: Re: [PATCH 2/2] cpufreq: cpu0: Extend support beyond CPU0

On 1 July 2014 00:03, Rob Herring <rob.herring@...aro.org> wrote:
>> What about comparing "clocks" property in cpu DT nodes?
>
> What if a different clock is selected for some reason.

I don't know why that will happen for CPUs sharing clock line.

> I think a clock api function would be better.

@Mike: What do you think? I think we can get a clock API for
this.

> That being said, I don't really have any issue with such a function.
> Some comments on the implementation.

>> +static int of_property_match(const struct device_node *np1,
>> +                             const struct device_node *np2,
>> +                             const char *list_name)
>> +{
>> +       const __be32 *list1, *list2, *list1_end;
>
> s/list/prop/
>
> Everywhere.

Ok.

>> +       int size1, size2;
>> +       phandle phandle1, phandle2;
>> +
>> +       /* Retrieve the list property */
>> +       list1 = of_get_property(np1, list_name, &size1);
>> +       if (!list1)
>> +               return -ENOENT;
>> +
>> +       list2 = of_get_property(np2, list_name, &size2);
>> +       if (!list2)
>> +               return -ENOENT;
>> +
>> +       if (size1 != size2)
>> +               return 0;
>> +
>> +       list1_end = list1 + size1 / sizeof(*list1);
>> +
>> +       /* Loop over the phandles */
>> +       while (list1 < list1_end) {
>> +               phandle1 = be32_to_cpup(list1++);
>> +               phandle2 = be32_to_cpup(list2++);
>> +
>> +               if (phandle1 != phandle2)
>> +                       return 0;
>> +       }
>
> You can just do a memcmp here.

Yeah, that would be much better.

> This is wrong anyway because you don't know #clock-cells size.

I was actually comparing all the clock-cells, whatever there number
is to make sure "clocks" properties are exactly same. Anyway
memcmp will still guarantee that.

Thanks for your review.
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