[PATCH 1/4][Eoan] ACPI/PPTT: Modify node flag detection to find last IDENTICAL

[dann frazier]

From: Jeremy Linton <jeremy.linton at arm.com>

BugLink: https://bugs.launchpad.net/bugs/1841490

The ACPI specification implies that the IDENTICAL flag should be
set on all non leaf nodes where the children are identical.
This means that we need to be searching for the last node with
the identical flag set rather than the first one.

Since this flag is also dependent on the table revision, we
need to add a bit of extra code to verify the table revision,
and the next node's state in the traversal. Since we want to
avoid function pointers here, lets just special case
the IDENTICAL flag.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Tested-by: Hanjun Guo <hanjun.guo at linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla at arm.com>
Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
Signed-off-by: Will Deacon <will at kernel.org>
(cherry picked from commit ed2b664fcc8073c09394393756df3fc86977bbac)
Signed-off-by: dann frazier <dann.frazier at canonical.com>
---
 drivers/acpi/pptt.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index b72e6afaa8fb9..05344413f1997 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -432,17 +432,40 @@ static void cache_setup_acpi_cpu(struct acpi_table_header *table,
 	}
 }
 
+static bool flag_identical(struct acpi_table_header *table_hdr,
+			   struct acpi_pptt_processor *cpu)
+{
+	struct acpi_pptt_processor *next;
+
+	/* heterogeneous machines must use PPTT revision > 1 */
+	if (table_hdr->revision < 2)
+		return false;
+
+	/* Locate the last node in the tree with IDENTICAL set */
+	if (cpu->flags & ACPI_PPTT_ACPI_IDENTICAL) {
+		next = fetch_pptt_node(table_hdr, cpu->parent);
+		if (!(next && next->flags & ACPI_PPTT_ACPI_IDENTICAL))
+			return true;
+	}
+
+	return false;
+}
+
 /* Passing level values greater than this will result in search termination */
 #define PPTT_ABORT_PACKAGE 0xFF
 
-static struct acpi_pptt_processor *acpi_find_processor_package_id(struct acpi_table_header *table_hdr,
-								  struct acpi_pptt_processor *cpu,
-								  int level, int flag)
+static struct acpi_pptt_processor *acpi_find_processor_tag(struct acpi_table_header *table_hdr,
+							   struct acpi_pptt_processor *cpu,
+							   int level, int flag)
 {
 	struct acpi_pptt_processor *prev_node;
 
 	while (cpu && level) {
-		if (cpu->flags & flag)
+		/* special case the identical flag to find last identical */
+		if (flag == ACPI_PPTT_ACPI_IDENTICAL) {
+			if (flag_identical(table_hdr, cpu))
+				break;
+		} else if (cpu->flags & flag)
 			break;
 		pr_debug("level %d\n", level);
 		prev_node = fetch_pptt_node(table_hdr, cpu->parent);
@@ -480,8 +503,8 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table,
 
 	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
 	if (cpu_node) {
-		cpu_node = acpi_find_processor_package_id(table, cpu_node,
-							  level, flag);
+		cpu_node = acpi_find_processor_tag(table, cpu_node,
+						   level, flag);
 		/*
 		 * As per specification if the processor structure represents
 		 * an actual processor, then ACPI processor ID must be valid.
-- 
2.23.0