Subject: Re: [PATCH] powerpc: Use ibm, chip-id property to compute cpu_core_mask if available

From: Vasant Hegde <[email-masked]>
Date: Fri, 09 Aug 2013 12:52:12 +0530

On 07/04/2013 08:35 AM, Paul Mackerras wrote:
> Some systems have an ibm,chip-id property in the cpu nodes in the
> device tree.  On these systems, we now use that to compute the
> cpu_core_mask (i.e. the set of core siblings) rather than looking
> at cache properties.
>

Paul,

I wanted to test this patch but not able to apply this patch on top of Linux 
tree. Looks like I'm missing traverse_core_siblings() related patch. I searched 
in ppc mailing list and couldn't figure out.

Can you point me to related patch?

-Vasant

> Signed-off-by: Paul Mackerras <[email-masked]>
> ---
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index b72d8c9..3b7a118 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -587,6 +587,32 @@ int cpu_first_thread_of_core(int core)
>   }
>   EXPORT_SYMBOL_GPL(cpu_first_thread_of_core);
>
> +static void traverse_siblings_chip_id(int cpu, int add, int chipid)
> +{
> +	const struct cpumask *mask;
> +	struct device_node *np;
> +	int i, plen;
> +	const int *prop;
> +
> +	mask = add ? cpu_online_mask : cpu_present_mask;
> +	for_each_cpu(i, mask) {
> +		np = of_get_cpu_node(i, NULL);
> +		if (!np)
> +			continue;
> +		prop = of_get_property(np, "ibm,chip-id", &plen);
> +		if (prop && plen == sizeof(int) && *prop == chipid) {
> +			if (add) {
> +				cpumask_set_cpu(cpu, cpu_core_mask(i));
> +				cpumask_set_cpu(i, cpu_core_mask(cpu));
> +			} else {
> +				cpumask_clear_cpu(cpu, cpu_core_mask(i));
> +				cpumask_clear_cpu(i, cpu_core_mask(cpu));
> +			}
> +		}
> +		of_node_put(np);
> +	}
> +}
> +
>   /* Must be called when no change can occur to cpu_present_mask,
>    * i.e. during cpu online or offline.
>    */
> @@ -611,14 +637,29 @@ static struct device_node *cpu_to_l2cache(int cpu)
>
>   static void traverse_core_siblings(int cpu, int add)
>   {
> -	struct device_node *l2_cache;
> +	struct device_node *l2_cache, *np;
>   	const struct cpumask *mask;
> -	int i;
> +	int i, chip, plen;
> +	const int *prop;
> +
> +	/* First see if we have ibm,chip-id properties in cpu nodes */
> +	np = of_get_cpu_node(cpu, NULL);
> +	if (np) {
> +		chip = -1;
> +		prop = of_get_property(np, "ibm,chip-id", &plen);
> +		if (prop && plen == sizeof(int))
> +			chip = *(int *)prop;
> +		of_node_put(np);
> +		if (chip >= 0) {
> +			traverse_siblings_chip_id(cpu, add, chip);
> +			return;
> +		}
> +	}
>
>   	l2_cache = cpu_to_l2cache(cpu);
>   	mask = add ? cpu_online_mask : cpu_present_mask;
>   	for_each_cpu(i, mask) {
> -		struct device_node *np = cpu_to_l2cache(i);
> +		np = cpu_to_l2cache(i);
>   		if (!np)
>   			continue;
>   		if (np == l2_cache) {
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