irqchip/gicv3-its: Use MADT ITS subtable to do PCI/MSI domain initialization

Let ACPI build ITS PCI MSI domain. ACPI code is responsible for retrieving
inner domain token and passing it on to its_pci_msi_init_one generic
init call.

IORT maintains list of registered domain tokens and allows to find
corresponding domain based on MADT ITS subtable ID info.

Signed-off-by: Tomasz Nowicki <[e-mail]>
Acked-by: Marc Zyngier <[e-mail]>
Reviewed-by: Hanjun Guo <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>

drivers/irqchip/irq-gic-v3-its-pci-msi.c

···
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/acpi_iort.h>
 #include <linux/msi.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
···
 	return 0;
 }
 
+#ifdef CONFIG_ACPI
+
+static int __init
+its_pci_msi_parse_madt(struct acpi_subtable_header *header,
+		       const unsigned long end)
+{
+	struct acpi_madt_generic_translator *its_entry;
+	struct fwnode_handle *dom_handle;
+	const char *node_name;
+	int err = -ENXIO;
+
+	its_entry = (struct acpi_madt_generic_translator *)header;
+	node_name = kasprintf(GFP_KERNEL, "ITS@0x%lx",
+			      (long)its_entry->base_address);
+	dom_handle = iort_find_domain_token(its_entry->translation_id);
+	if (!dom_handle) {
+		pr_err("%s: Unable to locate ITS domain handle\n", node_name);
+		goto out;
+	}
+
+	err = its_pci_msi_init_one(dom_handle, node_name);
+	if (!err)
+		pr_info("PCI/MSI: %s domain created\n", node_name);
+
+out:
+	kfree(node_name);
+	return err;
+}
+
+static int __init its_pci_acpi_msi_init(void)
+{
+	acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
+			      its_pci_msi_parse_madt, 0);
+	return 0;
+}
+#else
+static int __init its_pci_acpi_msi_init(void)
+{
+	return 0;
+}
+#endif
+
 static int __init its_pci_msi_init(void)
 {
 	its_pci_of_msi_init();
+	its_pci_acpi_msi_init();
 
 	return 0;
 }