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[PATCH 4/5] cacheinfo: Expose the code to generate a cache-id from a device_node

James Morse posted 5 patches 8 months ago
There is a newer version of this series
[PATCH 4/5] cacheinfo: Expose the code to generate a cache-id from a device_node
Posted by James Morse 8 months ago 
The MPAM driver identifies caches by id for use with resctrl. It
needs to know the cache-id when probe-ing, but the value isn't set
in cacheinfo until the corresponding CPU comes online.

Expose the code that generates the cache-id. This allows the MPAM
driver to determine the properties of the caches without waiting
for all CPUs to come online.

Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/base/cacheinfo.c  | 15 +++++++++++----
 include/linux/cacheinfo.h |  1 +
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index d8e5b4c7156c..6316d80abab8 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -188,7 +188,7 @@ static bool cache_node_is_unified(struct cacheinfo *this_leaf,
 #define arch_compact_of_hwid(_x)	(_x)
 #endif
 
-static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
+unsigned long cache_of_get_id(struct device_node *np)
 {
 	struct device_node *cpu;
 	u32 min_id = ~0;
@@ -200,7 +200,7 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
 		id = arch_compact_of_hwid(id);
 		if (FIELD_GET(GENMASK_ULL(63, 32), id)) {
 			of_node_put(cpu);
-			return;
+			return ~0UL;
 		}
 		while (1) {
 			if (!cache_node)
@@ -214,8 +214,15 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
 		}
 	}
 
-	if (min_id != ~0) {
-		this_leaf->id = min_id;
+	return min_id;
+}
+
+static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
+{
+	unsigned long id = cache_of_get_id(np);
+
+	if (id != ~0UL) {
+		this_leaf->id = id;
 		this_leaf->attributes |= CACHE_ID;
 	}
 }
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index c8f4f0a0b874..9c959caf8af8 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -112,6 +112,7 @@ int acpi_get_cache_info(unsigned int cpu,
 #endif
 
 const struct attribute_group *cache_get_priv_group(struct cacheinfo *this_leaf);
+unsigned long cache_of_get_id(struct device_node *np);
 
 /*
  * Get the cacheinfo structure for the cache associated with @cpu at
-- 
2.39.5
Re: [PATCH 4/5] cacheinfo: Expose the code to generate a cache-id from a device_node
Posted by Jonathan Cameron 7 months, 3 weeks ago 
On Fri, 13 Jun 2025 13:03:55 +0000
James Morse <james.morse@arm.com> wrote:

> The MPAM driver identifies caches by id for use with resctrl. It
> needs to know the cache-id when probe-ing, but the value isn't set
> in cacheinfo until the corresponding CPU comes online.
> 
> Expose the code that generates the cache-id. This allows the MPAM
> driver to determine the properties of the caches without waiting
> for all CPUs to come online.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
Feels to me like this needs to come with the user.
The earlier patches at least expose it via existing infrastructure
this isn't used at all yet...

> ---
>  drivers/base/cacheinfo.c  | 15 +++++++++++----
>  include/linux/cacheinfo.h |  1 +
>  2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index d8e5b4c7156c..6316d80abab8 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -188,7 +188,7 @@ static bool cache_node_is_unified(struct cacheinfo *this_leaf,
>  #define arch_compact_of_hwid(_x)	(_x)
>  #endif
>  
> -static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
> +unsigned long cache_of_get_id(struct device_node *np)
Bit confusing to have cache_of_set_id() call cache_of_get_id() like this because
they are in no way mirrors of each other.   Rename?
(and naturally I'm providing no suggestions :)

>  {
>  	struct device_node *cpu;
>  	u32 min_id = ~0;
> @@ -200,7 +200,7 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
>  		id = arch_compact_of_hwid(id);
>  		if (FIELD_GET(GENMASK_ULL(63, 32), id)) {
>  			of_node_put(cpu);
> -			return;
> +			return ~0UL;
>  		}
>  		while (1) {
>  			if (!cache_node)
> @@ -214,8 +214,15 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
>  		}
>  	}
>  
> -	if (min_id != ~0) {
> -		this_leaf->id = min_id;
> +	return min_id;
> +}
> +
> +static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
> +{
> +	unsigned long id = cache_of_get_id(np);
> +
> +	if (id != ~0UL) {
> +		this_leaf->id = id;
>  		this_leaf->attributes |= CACHE_ID;
>  	}
>  }
> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
> index c8f4f0a0b874..9c959caf8af8 100644
> --- a/include/linux/cacheinfo.h
> +++ b/include/linux/cacheinfo.h
> @@ -112,6 +112,7 @@ int acpi_get_cache_info(unsigned int cpu,
>  #endif
>  
>  const struct attribute_group *cache_get_priv_group(struct cacheinfo *this_leaf);
> +unsigned long cache_of_get_id(struct device_node *np);
>  
>  /*
>   * Get the cacheinfo structure for the cache associated with @cpu at
Re: [PATCH 4/5] cacheinfo: Expose the code to generate a cache-id from a device_node
Posted by James Morse 7 months, 2 weeks ago 
Hi Jonathan,

On 17/06/2025 17:21, Jonathan Cameron wrote:
> On Fri, 13 Jun 2025 13:03:55 +0000
> James Morse <james.morse@arm.com> wrote:

>> The MPAM driver identifies caches by id for use with resctrl. It
>> needs to know the cache-id when probe-ing, but the value isn't set
>> in cacheinfo until the corresponding CPU comes online.
>>
>> Expose the code that generates the cache-id. This allows the MPAM
>> driver to determine the properties of the caches without waiting
>> for all CPUs to come online.

> Feels to me like this needs to come with the user.
> The earlier patches at least expose it via existing infrastructure
> this isn't used at all yet...

Yeah, I'm damned whatever I do here. I can move this (and patch 5) to the series with the
MPAM driver - this was me trying to reduce the number of people that get copied on that,
and the number of trees that it touches...


>> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
>> index d8e5b4c7156c..6316d80abab8 100644
>> --- a/drivers/base/cacheinfo.c
>> +++ b/drivers/base/cacheinfo.c
>> @@ -188,7 +188,7 @@ static bool cache_node_is_unified(struct cacheinfo *this_leaf,
>>  #define arch_compact_of_hwid(_x)	(_x)
>>  #endif
>>  
>> -static void cache_of_set_id(struct cacheinfo *this_leaf, struct device_node *np)
>> +unsigned long cache_of_get_id(struct device_node *np)

> Bit confusing to have cache_of_set_id() call cache_of_get_id() like this because
> they are in no way mirrors of each other.   Rename?
> (and naturally I'm providing no suggestions :)

I'll try cache_of_calculate_id() ...


>>  {
>>  	struct device_node *cpu;
>>  	u32 min_id = ~0;


Thanks,

James

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