[PATCH v5] ACPI/IORT: Fix PMCG node single ID mapping handling

[Tuan Phan <tuanphan@os.amperecomputing.com>]

An IORT PMCG node can have no ID mapping if its overflow interrupt is
wire based therefore the code that parses the PMCG node can not assume
the node will always have a single mapping present at index 0.

Fix iort_get_id_mapping_index() by checking for an overflow interrupt
and mapping count.

Fixes: 24e516049360 ("ACPI/IORT: Add support for PMCG")

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Hanjun Guo <guoahanjun@huawei.com>
Signed-off-by: Tuan Phan <tuanphan@os.amperecomputing.com>
---
v1 -> v2:
- Use pmcg node to detect wired base overflow interrupt.

v2 -> v3:
- Address Hanjun and Robin's comments.

v3 -> v4:
- Update the title and description as mentioned by Lorenzo.

v4 -> v5:
- Remove period in the title and commit references.

 drivers/acpi/arm64/iort.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index ed3d2d1..12bb70e 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -414,6 +414,7 @@ static struct acpi_iort_node *iort_node_get_id(struct acpi_iort_node *node,
 static int iort_get_id_mapping_index(struct acpi_iort_node *node)
 {
 	struct acpi_iort_smmu_v3 *smmu;
+	struct acpi_iort_pmcg *pmcg;
 
 	switch (node->type) {
 	case ACPI_IORT_NODE_SMMU_V3:
@@ -441,6 +442,10 @@ static int iort_get_id_mapping_index(struct acpi_iort_node *node)
 
 		return smmu->id_mapping_index;
 	case ACPI_IORT_NODE_PMCG:
+		pmcg = (struct acpi_iort_pmcg *)node->node_data;
+		if (pmcg->overflow_gsiv || node->mapping_count == 0)
+			return -EINVAL;
+
 		return 0;
 	default:
 		return -EINVAL;
-- 
2.7.4