The MPAM driver needs to know the size of a cache associated with a
particular CPU. The DT/ACPI agnostic way of doing this is to ask cacheinfo.

Add a helper to do this.

Signed-off-by: James Morse <james.morse@arm.com>
---
 include/linux/cacheinfo.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index 9c959caf8af8..3f1b6b2e25b5 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -148,6 +148,26 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
 	return ci ? ci->id : -1;
 }
 
+/*
+ * Get the size of the cache associated with @cpu at level @level.
+ * cpuhp lock must be held.
+ */
+static inline unsigned int get_cpu_cacheinfo_size(int cpu, int level)
+{
+	struct cpu_cacheinfo *ci = get_cpu_cacheinfo(cpu);
+	int i;
+
+	if (!ci->info_list)
+		return 0;
+
+	for (i = 0; i < ci->num_leaves; i++) {
+		if (ci->info_list[i].level == level)
+			return ci->info_list[i].size;
+	}
+
+	return 0;
+}
+
 #if defined(CONFIG_ARM64) || defined(CONFIG_ARM)
 #define use_arch_cache_info()	(true)
 #else
-- 
2.39.5

On Fri, 13 Jun 2025 13:03:56 +0000
James Morse <james.morse@arm.com> wrote:

> The MPAM driver needs to know the size of a cache associated with a
> particular CPU. The DT/ACPI agnostic way of doing this is to ask cacheinfo.
> 
> Add a helper to do this.
> 
> Signed-off-by: James Morse <james.morse@arm.com>



> ---
>  include/linux/cacheinfo.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
> index 9c959caf8af8..3f1b6b2e25b5 100644
> --- a/include/linux/cacheinfo.h
> +++ b/include/linux/cacheinfo.h
> @@ -148,6 +148,26 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
>  	return ci ? ci->id : -1;
>  }
>  
> +/*
> + * Get the size of the cache associated with @cpu at level @level.
> + * cpuhp lock must be held.
To me kernel-doc would be appropriate.  Particularly the return 0 thing.
However there isn't any for existing cacheinfo interfaces so maybe
fair enough to 'follow local style' on that.

> + */
> +static inline unsigned int get_cpu_cacheinfo_size(int cpu, int level)
> +{
> +	struct cpu_cacheinfo *ci = get_cpu_cacheinfo(cpu);
> +	int i;
> +
> +	if (!ci->info_list)
> +		return 0;
> +
> +	for (i = 0; i < ci->num_leaves; i++) {
> +		if (ci->info_list[i].level == level)
> +			return ci->info_list[i].size;
> +	}
> +
> +	return 0;
> +}
> +
Why not

static inline unsigned int get_cpu_cacheinfo_size(int cpu, int level)
{
	struct cpu_cachinfo *ci = get_cpu_cacheinfo_level(cpu, lev);

	return ci ? ci->size; 0;
}

Like existing get_cpu_cacheinfo_id()?

>  #if defined(CONFIG_ARM64) || defined(CONFIG_ARM)
>  #define use_arch_cache_info()	(true)
>  #else

Hi Jonathan,

On 17/06/2025 17:28, Jonathan Cameron wrote:
> On Fri, 13 Jun 2025 13:03:56 +0000
> James Morse <james.morse@arm.com> wrote:
> 
>> The MPAM driver needs to know the size of a cache associated with a
>> particular CPU. The DT/ACPI agnostic way of doing this is to ask cacheinfo.
>>
>> Add a helper to do this.

>> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
>> index 9c959caf8af8..3f1b6b2e25b5 100644
>> --- a/include/linux/cacheinfo.h
>> +++ b/include/linux/cacheinfo.h
>> @@ -148,6 +148,26 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
>>  	return ci ? ci->id : -1;
>>  }
>>  
>> +/*
>> + * Get the size of the cache associated with @cpu at level @level.
>> + * cpuhp lock must be held.

> To me kernel-doc would be appropriate.  Particularly the return 0 thing.
> However there isn't any for existing cacheinfo interfaces so maybe
> fair enough to 'follow local style' on that.

Documentation should be the direction of travel right? I'll change this.


>> + */
>> +static inline unsigned int get_cpu_cacheinfo_size(int cpu, int level)
>> +{
>> +	struct cpu_cacheinfo *ci = get_cpu_cacheinfo(cpu);
>> +	int i;
>> +
>> +	if (!ci->info_list)
>> +		return 0;
>> +
>> +	for (i = 0; i < ci->num_leaves; i++) {
>> +		if (ci->info_list[i].level == level)
>> +			return ci->info_list[i].size;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
> Why not
> 
> static inline unsigned int get_cpu_cacheinfo_size(int cpu, int level)
> {
> 	struct cpu_cachinfo *ci = get_cpu_cacheinfo_level(cpu, lev);
> 
> 	return ci ? ci->size; 0;
> }
> 
> Like existing get_cpu_cacheinfo_id()?

I've been dragging this around for years. Fixed.


Thanks!

James