linux-kernel - [PATCH v3 4/4] cacheinfo: Add use_arch[|_cache]

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Date:   Thu, 13 Apr 2023 11:14:34 +0200
From:   Pierre Gondois <pierre.gondois@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Radu Rendec <rrendec@...hat.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Will Deacon <will@...nel.org>,
        Pierre Gondois <pierre.gondois@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>
Subject: [PATCH v3 4/4] cacheinfo: Add use_arch[|_cache]_info field/function

The cache information can be extracted from either a Device
Tree (DT), the PPTT ACPI table, or arch registers (clidr_el1
for arm64).

The clidr_el1 register is used only if DT/ACPI information is not
available. It does not states how caches are shared among CPUs.

Add a use_arch_cache_info field/function to identify when the
DT/ACPI doesn't provide cache information. Use this information
to assume L1 caches are privates and L2 and higher are shared among
all CPUs.

Signed-off-by: Pierre Gondois <pierre.gondois@....com>
---
 drivers/base/cacheinfo.c  | 13 ++++++++++++-
 include/linux/cacheinfo.h | 10 ++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 06de9a468958..49dbb4357911 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -40,7 +40,8 @@ static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
 	 * For non DT/ACPI systems, assume unique level 1 caches,
 	 * system-wide shared caches for all other levels.
 	 */
-	if (!(IS_ENABLED(CONFIG_OF) || IS_ENABLED(CONFIG_ACPI)))
+	if (!(IS_ENABLED(CONFIG_OF) || IS_ENABLED(CONFIG_ACPI)) ||
+	    this_leaf->use_arch_info)
 		return (this_leaf->level != 1) && (sib_leaf->level != 1);
 
 	if ((sib_leaf->attributes & CACHE_ID) &&
@@ -349,6 +350,7 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	struct cacheinfo *this_leaf, *sib_leaf;
 	unsigned int index, sib_index;
+	bool use_arch_info = false;
 	int ret = 0;
 
 	if (this_cpu_ci->cpu_map_populated)
@@ -361,6 +363,12 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
 	 */
 	if (!last_level_cache_is_valid(cpu)) {
 		ret = cache_setup_properties(cpu);
+		if (ret && use_arch_cache_info()) {
+			// Possibility to rely on arch specific information.
+			use_arch_info = true;
+			ret = 0;
+		}
+
 		if (ret)
 			return ret;
 	}
@@ -370,6 +378,9 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
 
 		this_leaf = per_cpu_cacheinfo_idx(cpu, index);
 
+		if (use_arch_info)
+			this_leaf->use_arch_info = true;
+
 		cpumask_set_cpu(cpu, &this_leaf->shared_cpu_map);
 		for_each_online_cpu(i) {
 			struct cpu_cacheinfo *sib_cpu_ci = get_cpu_cacheinfo(i);
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index 908e19d17f49..fed675b251a2 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -66,6 +66,7 @@ struct cacheinfo {
 #define CACHE_ALLOCATE_POLICY_MASK	\
 	(CACHE_READ_ALLOCATE | CACHE_WRITE_ALLOCATE)
 #define CACHE_ID		BIT(4)
+	bool use_arch_info;
 	void *fw_token;
 	bool disable_sysfs;
 	void *priv;
@@ -129,4 +130,13 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
 	return -1;
 }
 
+static inline bool use_arch_cache_info(void)
+{
+#if defined(CONFIG_ARM64)
+	return true;
+#else
+	return false;
+#endif
+}
+
 #endif /* _LINUX_CACHEINFO_H */
-- 
2.25.1