[PATCH v4 5/8] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control

[Kohei Tarumizu]

Create a cache sysfs directory without ACPI PPTT if the
CONFIG_HWPF_CONTROL is true.

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 at fujitsu.com>
---
 arch/arm64/kernel/cacheinfo.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/arch/arm64/kernel/cacheinfo.c b/arch/arm64/kernel/cacheinfo.c
index 587543c6c51c..039ec32d0b3d 100644
--- a/arch/arm64/kernel/cacheinfo.c
+++ b/arch/arm64/kernel/cacheinfo.c
@@ -43,6 +43,21 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
 	this_leaf->type = type;
 }
 
+#if defined(CONFIG_HWPF_CONTROL)
+static 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;
+}
+#endif
+
 int init_cache_level(unsigned int cpu)
 {
 	unsigned int ctype, level, leaves, fw_level;
@@ -95,5 +110,19 @@ int populate_cache_leaves(unsigned int cpu)
 			ci_leaf_init(this_leaf++, type, level);
 		}
 	}
+
+#if defined(CONFIG_HWPF_CONTROL)
+	/*
+	 * 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.
+	 **/
+	if (!acpi_disabled)
+		if (!acpi_has_pptt())
+			this_cpu_ci->cpu_map_populated = true;
+#endif
+
 	return 0;
 }
-- 
2.27.0