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

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Date:	Mon, 30 Jun 2014 13:27:52 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Mike Turquette <mturquette@...aro.org>,
	Rob Herring <rob.herring@...aro.org>,
	Grant Likely <grant.likely@...aro.org>
Cc:	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 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?

@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;
+       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;
+       }
+
+       return 1;
+}

@Stephen: I have updated my tree with this change, in case you wanna
try.
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