[PATCH 03/33] ACPI / PPTT: Add a helper to fill a cpumask from a processor container

[James Morse <james.morse@arm.com>]

The PPTT describes CPUs and caches, as well as processor containers.
The ACPI table for MPAM describes the set of CPUs that can access an MSC
with the UID of a processor container.

Add a helper to find the processor container by its id, then walk
the possible CPUs to fill a cpumask with the CPUs that have this
processor container as a parent.

CC: Dave Martin <dave.martin@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since RFC:
 * Dropped has_leaf_flag dodging of acpi_pptt_leaf_node()
 * Added missing : in kernel-doc
 * Made helper return void as this never actually returns an error.
---
 drivers/acpi/pptt.c  | 86 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h |  3 ++
 2 files changed, 89 insertions(+)

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 54676e3d82dd..4791ca2bdfac 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -298,6 +298,92 @@ static struct acpi_pptt_processor *acpi_find_processor_node(struct acpi_table_he
 	return NULL;
 }
 
+/**
+ * acpi_pptt_get_child_cpus() - Find all the CPUs below a PPTT processor node
+ * @table_hdr:		A reference to the PPTT table.
+ * @parent_node:	A pointer to the processor node in the @table_hdr.
+ * @cpus:		A cpumask to fill with the CPUs below @parent_node.
+ *
+ * Walks up the PPTT from every possible CPU to find if the provided
+ * @parent_node is a parent of this CPU.
+ */
+static void acpi_pptt_get_child_cpus(struct acpi_table_header *table_hdr,
+				     struct acpi_pptt_processor *parent_node,
+				     cpumask_t *cpus)
+{
+	struct acpi_pptt_processor *cpu_node;
+	u32 acpi_id;
+	int cpu;
+
+	cpumask_clear(cpus);
+
+	for_each_possible_cpu(cpu) {
+		acpi_id = get_acpi_id_for_cpu(cpu);
+		cpu_node = acpi_find_processor_node(table_hdr, acpi_id);
+
+		while (cpu_node) {
+			if (cpu_node == parent_node) {
+				cpumask_set_cpu(cpu, cpus);
+				break;
+			}
+			cpu_node = fetch_pptt_node(table_hdr, cpu_node->parent);
+		}
+	}
+}
+
+/**
+ * acpi_pptt_get_cpus_from_container() - Populate a cpumask with all CPUs in a
+ *                                       processor containers
+ * @acpi_cpu_id:	The UID of the processor container.
+ * @cpus:		The resulting CPU mask.
+ *
+ * Find the specified Processor Container, and fill @cpus with all the cpus
+ * below it.
+ *
+ * Not all 'Processor' entries in the PPTT are either a CPU or a Processor
+ * Container, they may exist purely to describe a Private resource. CPUs
+ * have to be leaves, so a Processor Container is a non-leaf that has the
+ * 'ACPI Processor ID valid' flag set.
+ *
+ * Return: 0 for a complete walk, or an error if the mask is incomplete.
+ */
+void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus)
+{
+	struct acpi_pptt_processor *cpu_node;
+	struct acpi_table_header *table_hdr;
+	struct acpi_subtable_header *entry;
+	unsigned long table_end;
+	acpi_status status;
+	bool leaf_flag;
+	u32 proc_sz;
+
+	cpumask_clear(cpus);
+
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table_hdr);
+	if (ACPI_FAILURE(status))
+		return;
+
+	table_end = (unsigned long)table_hdr + table_hdr->length;
+	entry = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr,
+			     sizeof(struct acpi_table_pptt));
+	proc_sz = sizeof(struct acpi_pptt_processor);
+	while ((unsigned long)entry + proc_sz <= table_end) {
+		cpu_node = (struct acpi_pptt_processor *)entry;
+		if (entry->type == ACPI_PPTT_TYPE_PROCESSOR &&
+		    cpu_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID) {
+			leaf_flag = acpi_pptt_leaf_node(table_hdr, cpu_node);
+			if (!leaf_flag) {
+				if (cpu_node->acpi_processor_id == acpi_cpu_id)
+					acpi_pptt_get_child_cpus(table_hdr, cpu_node, cpus);
+			}
+		}
+		entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry,
+				     entry->length);
+	}
+
+	acpi_put_table(table_hdr);
+}
+
 static u8 acpi_cache_type(enum cache_type type)
 {
 	switch (type) {
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 1c5bb1e887cd..f97a9ff678cc 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1541,6 +1541,7 @@ int find_acpi_cpu_topology(unsigned int cpu, int level);
 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);
+void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus);
 #else
 static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
 {
@@ -1562,6 +1563,8 @@ static inline int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
 {
 	return -EINVAL;
 }
+static inline void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id,
+						     cpumask_t *cpus) { }
 #endif
 
 void acpi_arch_init(void);
-- 
2.20.1