1 files changed, 55 insertions, 2 deletions

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 33f71983e001..6078064684c6 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -298,6 +298,59 @@ out:
 	return status;
 }
 
+struct iort_workaround_oem_info {
+	char oem_id[ACPI_OEM_ID_SIZE + 1];
+	char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1];
+	u32 oem_revision;
+};
+
+static bool apply_id_count_workaround;
+
+static struct iort_workaround_oem_info wa_info[] __initdata = {
+	{
+		.oem_id		= "HISI  ",
+		.oem_table_id	= "HIP07   ",
+		.oem_revision	= 0,
+	}, {
+		.oem_id		= "HISI  ",
+		.oem_table_id	= "HIP08   ",
+		.oem_revision	= 0,
+	}
+};
+
+static void __init
+iort_check_id_count_workaround(struct acpi_table_header *tbl)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(wa_info); i++) {
+		if (!memcmp(wa_info[i].oem_id, tbl->oem_id, ACPI_OEM_ID_SIZE) &&
+		    !memcmp(wa_info[i].oem_table_id, tbl->oem_table_id, ACPI_OEM_TABLE_ID_SIZE) &&
+		    wa_info[i].oem_revision == tbl->oem_revision) {
+			apply_id_count_workaround = true;
+			pr_warn(FW_BUG "ID count for ID mapping entry is wrong, applying workaround\n");
+			break;
+		}
+	}
+}
+
+static inline u32 iort_get_map_max(struct acpi_iort_id_mapping *map)
+{
+	u32 map_max = map->input_base + map->id_count;
+
+	/*
+	 * The IORT specification revision D (Section 3, table 4, page 9) says
+	 * Number of IDs = The number of IDs in the range minus one, but the
+	 * IORT code ignored the "minus one", and some firmware did that too,
+	 * so apply a workaround here to keep compatible with both the spec
+	 * compliant and non-spec compliant firmwares.
+	 */
+	if (apply_id_count_workaround)
+		map_max--;
+
+	return map_max;
+}
+
 static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
 		       u32 *rid_out)
 {
@@ -314,8 +367,7 @@ static int iort_id_map(struct acpi_iort_id_mapping *map, u8 type, u32 rid_in,
 		return -ENXIO;
 	}
 
-	if (rid_in < map->input_base ||
-	    (rid_in >= map->input_base + map->id_count))
+	if (rid_in < map->input_base || rid_in > iort_get_map_max(map))
 		return -ENXIO;
 
 	*rid_out = map->output_base + (rid_in - map->input_base);
@@ -1631,5 +1683,6 @@ void __init acpi_iort_init(void)
 		return;
 	}
 
+	iort_check_id_count_workaround(iort_table);
 	iort_init_platform_devices();
 }