[PATCH v5 3/6] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control

[Kohei Tarumizu]

Create a cache sysfs directory without ACPI PPTT if the CPU model is
A64FX and CONFIG_ALLOW_INCOMPLETE_CACHE_SYSFS is true. Currentry,
CONFIG_ALLOW_INCOMPLETE_CACHE_SYSFS is set only when
CONFIG_A64FX_HWPF_CONTROL is enabled.

Hardware prefetch control driver need cache sysfs directory and cache
level/type information. In ARM processor, these information can be
obtained from the register even without PPTT.

This patch set the cpu_map_populated to true if the machine doesn't
have PPTT. It use only the level/type information obtained from
CLIDR_EL1, and don't use CCSIDR information.

Signed-off-by: Kohei Tarumizu <tarumizu.kohei@xxxxxxxxxxx>
---
 arch/arm64/kernel/cacheinfo.c | 27 +++++++++++++++++++++++++++
 drivers/acpi/pptt.c           | 18 ++++++++++++++++++
 include/linux/acpi.h          |  5 +++++
 include/linux/cacheinfo.h     | 10 ++++++++++
 4 files changed, 60 insertions(+)

diff --git a/arch/arm64/kernel/cacheinfo.c b/arch/arm64/kernel/cacheinfo.c
index 587543c6c51c..3b337a425acb 100644
--- a/arch/arm64/kernel/cacheinfo.c
+++ b/arch/arm64/kernel/cacheinfo.c
@@ -43,6 +43,30 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
 	this_leaf->type = type;
 }
 
+static const struct midr_range allow_list[] = {
+	MIDR_ALL_VERSIONS(MIDR_FUJITSU_A64FX),
+};
+
+/*
+ * This function works only for FUJITSU A64FX processor.
+ * If CONFIG_ALLOW_INCOMPLETE_CACHE_SYSFS is not defined, do nothing.
+ *
+ * Hardware prefetch functions need cache sysfs directory and cache
+ * level/type information. In ARM processor, these information can be
+ * obtained from registers even without PPTT. Therefore, we set the
+ * cpu_map_populated to true to create cache sysfs directory, if the
+ * machine doesn't have PPTT.
+ */
+static void allow_incomplete_cache_sysfs(struct cpu_cacheinfo *cpu_ci)
+{
+	if (!is_midr_in_range_list(read_cpuid_id(), allow_list))
+		return;
+
+	if (!acpi_disabled)
+		if (!acpi_has_pptt())
+			enable_cpu_map_populated(cpu_ci);
+}
+
 int init_cache_level(unsigned int cpu)
 {
 	unsigned int ctype, level, leaves, fw_level;
@@ -95,5 +119,8 @@ int populate_cache_leaves(unsigned int cpu)
 			ci_leaf_init(this_leaf++, type, level);
 		}
 	}
+
+	allow_incomplete_cache_sysfs(this_cpu_ci);
+
 	return 0;
 }
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 701f61c01359..fcd7295b81d7 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -838,3 +838,21 @@ int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
 	return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
 					  ACPI_PPTT_ACPI_IDENTICAL);
 }
+
+/**
+ * acpi_has_pptt() - Determine if ACPI has PPTT table or not
+ *
+ * Return: true if ACPI has PPTT, false if ACPI doesn't have PPTT.
+ */
+bool acpi_has_pptt(void)
+{
+	struct acpi_table_header *table;
+	acpi_status status;
+
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
+	if (ACPI_FAILURE(status))
+		return false;
+
+	acpi_put_table(table);
+	return true;
+}
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index d7136d13aa44..9daea11edad7 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1391,6 +1391,7 @@ int find_acpi_cpu_topology_cluster(unsigned int cpu);
 int find_acpi_cpu_topology_package(unsigned int cpu);
 int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
 int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
+bool acpi_has_pptt(void);
 #else
 static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
 {
@@ -1416,6 +1417,10 @@ static inline int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
 {
 	return -EINVAL;
 }
+static inline bool acpi_has_pptt(void)
+{
+	return false;
+}
 #endif
 
 #ifdef CONFIG_ACPI_PCC
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index 4ff37cb763ae..71f89da6792b 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -99,6 +99,16 @@ static inline int acpi_find_last_cache_level(unsigned int cpu)
 int acpi_find_last_cache_level(unsigned int cpu);
 #endif
 
+#ifndef CONFIG_ALLOW_INCOMPLETE_CACHE_SYSFS
+#define enable_cpu_map_populated(cpu_ci)
+#else
+static inline void enable_cpu_map_populated(struct cpu_cacheinfo *cpu_ci)
+{
+	cpu_ci->cpu_map_populated = true;
+}
+#endif
+
+
 const struct attribute_group *cache_get_priv_group(struct cacheinfo *this_leaf);
 
 /*
-- 
2.27.0