+static void acpi_init_coherency(struct acpi_device *adev)
+{
+ unsigned long long cca = 0;
+ acpi_status status;
+ struct acpi_device *parent = adev->parent;
+
+ if (parent && parent->flags.cca_seen) {
+ /*
+ * From ACPI spec, OSPM will ignore _CCA if an ancestor
+ * already saw one.
+ */
+ adev->flags.cca_seen = 1;
+ cca = parent->flags.coherent_dma;
+ } else {
+ status = acpi_evaluate_integer(adev->handle, "_CCA",
+ NULL, &cca);
+ if (ACPI_SUCCESS(status))
+ adev->flags.cca_seen = 1;
+ else if (!IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED))
+ /*
+ * If architecture does not specify that _CCA is
+ * required for DMA-able devices (e.g. x86),
+ * we default to _CCA=1.
+ */
+ cca = 1;
+ else
+ acpi_handle_debug(adev->handle,
+ "ACPI device is missing _CCA.\n");
+ }
+
+ adev->flags.coherent_dma = cca;
+}
+