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
© 2016 - 2026 Red Hat, Inc.