Subject: Re: [RFC PATCH v2 4/4] of: move of_get_cpu_node implementation to DT core library

From: Sudeep KarkadaNagesha <[email-masked]>
Date: Mon, 19 Aug 2013 14:24:20 +0100

On 19/08/13 14:11, Rob Herring wrote:
> On 08/16/2013 12:39 PM, Sudeep KarkadaNagesha wrote:
>> From: Sudeep KarkadaNagesha <[email-masked]>
>>
>> This patch moves the generalized implementation of of_get_cpu_node from
>> PowerPC to DT core library, thereby adding support for retrieving cpu
>> node for a given logical cpu index on any architecture.
>>
>> The CPU subsystem can now use this function to assign of_node in the
>> cpu device while registering CPUs.
>>
>> It is recommended to use these helper function only in pre-SMP/early
>> initialisation stages to retrieve CPU device node pointers in logical
>> ordering. Once the cpu devices are registered, it can be retrieved easily
>> from cpu device of_node which avoids unnecessary parsing and matching.
>>
>> Cc: Rob Herring <[email-masked]>
>> Cc: Grant Likely <[email-masked]>
>> Cc: Benjamin Herrenschmidt <[email-masked]>
>> Signed-off-by: Sudeep KarkadaNagesha <[email-masked]>
> 
> [snip]
> 
>> +/**
>> + * of_get_cpu_node - Get device node associated with the given logical CPU
>> + *
>> + * @cpu: CPU number(logical index) for which device node is required
>> + * @thread: if not NULL, local thread number within the physical core is
>> + *          returned
>> + *
>> + * The main purpose of this function is to retrieve the device node for the
>> + * given logical CPU index. It should be used to initialize the of_node in
>> + * cpu device. Once of_node in cpu device is populated, all the further
>> + * references can use that instead.
>> + *
>> + * CPU logical to physical index mapping is architecture specific and is built
>> + * before booting secondary cores. This function uses arch_match_cpu_phys_id
>> + * which can be overridden by architecture specific implementation.
>> + *
>> + * Returns a node pointer for the logical cpu if found, else NULL.
>> + */
>> +struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
>> +{
>> +	struct device_node *cpun, *cpus;
>> +
>> +	cpus = of_find_node_by_path("/cpus");
>> +	if (!cpus) {
>> +		pr_warn("Missing cpus node, bailing out\n");
>> +		return NULL;
>> +	}
>> +
>> +	for_each_child_of_node(cpus, cpun) {
>> +		if (of_node_cmp(cpun->type, "cpu"))
>> +			continue;
>> +#ifdef CONFIG_PPC
> 
> You don't really need this ifdef as this function should never succeed
> on other arches. Alternatively, you can use "IS_ENABLED(CONFIG_PPC)"
> instead.
> 
Agreed, I can remove it as long as no other architecture use that
property. It's just to avoid checking for it on other architectures.
I will use IS_ENABLED as you suggested.

> Otherwise,
> 
> Acked-by: Rob Herring <[email-masked]>
> 
Thanks.

Regards,
Sudeep