[QUESTION] Arm64: Query L3 cache info via DT

[Sudeep Holla]

Hi Tan,

On 28/12/16 03:42, Tan Xiaojun wrote:
> Hi.
> 
> I saw you discussed how to achieve querying cache information and
> tend to implement the external ones(like L3 cache) via DT a few
> months ago.
> 
> http://lists.infradead.org/pipermail/linux-arm-kernel/2016-February/405399.html
>
>  Are these implementations progressing? Forgive me to take the
> liberty to ask, we care about this thing.
> 

Yes the support to override the cache properties for DT was added in v4.10

However, it still depends on the the sysreg to get the total levels of
caches supported in the system. You may need to tweak a bit around that
to support what you need.

> If you've already implemented some codes, we can help with testing
> (in Hisilicon D02, D03, D05) after you send it to the mail-list.
> 

Sure, that would help.

> We can try our best to help if there is any difficulty.

OK, you can start trying the patch below :). It's not even compile
tested, so you make have to make some changes necessary. I just wanted
to put my thoughts here. Make sure all the L3 cacheinfo is present in DT.

Regards,
Sudeep


--

diff --git i/arch/arm64/kernel/cacheinfo.c w/arch/arm64/kernel/cacheinfo.c
index 9617301f76b5..88fbcd368104 100644
--- i/arch/arm64/kernel/cacheinfo.c
+++ w/arch/arm64/kernel/cacheinfo.c
@@ -84,7 +84,7 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,

 static int __init_cache_level(unsigned int cpu)
 {
-	unsigned int ctype, level, leaves;
+	unsigned int ctype, level, leaves, of_level;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);

 	for (level = 1, leaves = 0; level <= MAX_CACHE_LEVEL; level++) {
@@ -97,6 +97,17 @@ static int __init_cache_level(unsigned int cpu)
 		leaves += (ctype == CACHE_TYPE_SEPARATE) ? 2 : 1;
 	}

+	of_level = of_count_cache_levels(cpu);
+	if (level < of_level) {
+		/*
+		 * some external caches not specified in CLIDR_EL1
+		 * the information may be available in the device tree
+		 * only unified external caches are considered here
+		 */
+		level = of_level;
+		leaves += (of_level - level);
+	}
+
 	this_cpu_ci->num_levels = level;
 	this_cpu_ci->num_leaves = leaves;
 	return 0;
diff --git i/drivers/of/base.c w/drivers/of/base.c
index d4bea3c797d6..8007f3b06cb8 100644
--- i/drivers/of/base.c
+++ w/drivers/of/base.c
@@ -2267,6 +2267,20 @@ struct device_node *of_find_next_cache_node(const
struct device_node *np)
 	return NULL;
 }

+int of_count_cache_levels(unsigned int cpu)
+{
+	int level = 0;
+	struct device *cpu_dev = get_cpu_device(cpu);
+	struct device_node *np = cpu_dev->of_node;
+
+	while (np) {
+		level++;
+		np = of_find_next_cache_node(np);
+	}
+
+	return level;
+}
+
 /**
  * of_graph_parse_endpoint() - parse common endpoint node properties
  * @node: pointer to endpoint device_node
diff --git i/include/linux/of.h w/include/linux/of.h
index d72f01009297..c8597ae71ff3 100644
--- i/include/linux/of.h
+++ w/include/linux/of.h
@@ -280,6 +280,7 @@ extern struct device_node
*of_get_child_by_name(const struct device_node *node,

 /* cache lookup */
 extern struct device_node *of_find_next_cache_node(const struct
device_node *);
+extern int of_count_cache_levels(unsigned int cpu);
 extern struct device_node *of_find_node_with_property(
 	struct device_node *from, const char *prop_name);