linux-kernel - Re: [RFC PATCH 02/11] ARM: DT/kernel: define ARM specific arch_of_get_cpu

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Date:	Mon, 15 Jul 2013 14:10:59 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Sudeep.KarkadaNagesha@....com
CC:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, lorenzo.pieralisi@....com,
	linux@....linux.org.uk, arnd@...db.de, viresh.kumar@...aro.org,
	rob.herring@...xeda.com, rjw@...k.pl, grant.likely@...aro.org,
	cpufreq@...r.kernel.org, kernel@...gutronix.de,
	gregkh@...uxfoundation.org, olof@...om.net,
	gregory.clement@...e-electrons.com, shawn.guo@...aro.org
Subject: Re: [RFC PATCH 02/11] ARM: DT/kernel: define ARM specific arch_of_get_cpu_node

On 07/15/2013 05:22 AM, Sudeep.KarkadaNagesha@....com wrote:
> From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
> 
> CPU subsystem now provides architecture specific hook to retrieve the
> of_node. Most of the cpu DT node parsing and initialisation is contained
> in devtree.c. It's better to contain all CPU device node parsing there.
> 
> arch_of_get_cpu_node is mainly used to assign cpu->of_node when CPUs get
> registered. This patch overrides the defination of the same. It can also
> act as the helper function in pre-SMP/early initialisation stages to
> retrieve CPU device node pointers in logical ordering.
> 
> This mainly helps to avoid replication of the code doing CPU node parsing
> and physical(MPIDR) to logical mapping.
> 
> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>

[snip]

> +struct device_node * __init arch_of_get_cpu_node(int cpu)
> +{
> +	struct device_node *cpun, *cpus;
> +	const u32 *cell;
> +	u64 hwid;
> +	int ac;
> +
> +	cpus = of_find_node_by_path("/cpus");
> +	if (WARN(!cpus, "Missing cpus node, bailing out\n"))
> +		return NULL;
> +
> +	if (WARN_ON(of_property_read_u32(cpus, "#address-cells", &ac)))
> +		ac = of_n_addr_cells(cpus);
> +
> +	for_each_child_of_node(cpus, cpun) {
> +		if (of_node_cmp(cpun->type, "cpu"))
> +			continue;
> +		cell = of_get_property(cpun, "reg", NULL);
> +		if (WARN(!cell, "%s: missing reg property\n", cpun->full_name))
> +			continue;
> +
> +		hwid = of_read_number(cell, ac);
> +		if ((hwid & MPIDR_HWID_BITMASK) == cpu_logical_map(cpu))

Most of this function is not ARM specific, so it would be nice if we
could shrink the arch specific part down to just this match. A default
match of reg == logical cpu number might be useful.

The powermac cpufreq driver could probably also be converted
(arch/powerpc/platforms/powermac/cpufreq_64.c).

Other than that, this series looks good to me.

Rob

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