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

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Message-ID: <CABGGiswMuofH5WRh4jgwh1=CV+fEXM_Ec3+WNwThbuMLVxsdcg@mail.gmail.com>
Date:	Mon, 30 Jun 2014 13:33:59 -0500
From:	Rob Herring <rob.herring@...aro.org>
To:	Viresh Kumar <viresh.kumar@...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 Mon, Jun 30, 2014 at 2:57 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 27 June 2014 07:45, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>> On 27 June 2014 07:23, Mike Turquette <mturquette@...aro.org> wrote:
>>>> but it isn't future-proof if/when the clock framework starts returning
>>>> dynamically allocated clock pointers for each clk_get() invocation.
>>>> Maybe we need a function in the common clock framework that tells us if
>>>> the clocks are the same either via DT or by taking two clock pointers?
>>>
>>> I looked through the patch briefly and did not see why we would need to
>>> do this. Any hint?
>>
>> We want to know which CPUs are sharing clock line, so that we can
>> fill affected-cpus field of cpufreq core.
>
> What about comparing "clocks" property in cpu DT nodes?

What if a different clock is selected for some reason. I think a clock
api function would be better.

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

>
> @Rob/Grant: I tried looking for an existing routine to do that, but couldn't
> find it. And so wrote one.
>
> I am not good at DT stuff and so I do hope there would be few correction
> required here. Let me know if this can be added to drivers/of/base.c :
>
> +/**
> + * of_property_match - Match property in two nodes
> + * @np1, np2: Nodes to match
> + * @list_name: property to match
> + *
> + * Returns 1 on match, 0 on no match, and error for missing property.
> + */
> +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.

> +       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.

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

Rob
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