i2c / ACPI: Rework I2C device scanning

The way we currently scan I2C devices behind an I2C host controller does not
work in cases where the I2C device in question is not declared directly below
the host controller ACPI node.

This is perfectly legal according the ACPI 6.0 specification and some existing
systems are doing this.

To be able to enumerate all devices which are connected to a certain I2C host
controller we need to rework the current I2C scanning routine a bit. Instead of
scanning directly below the host controller we scan the whole ACPI namespace
for present devices with valid I2cSerialBus() connection pointing to the host
controller in question.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Dustin Byford <dustin@cumulusnetworks.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core.c

@@ -99,27 +99,40 @@ struct gsb_buffer {
 	};
 } __packed;
 
-static int acpi_i2c_add_resource(struct acpi_resource *ares, void *data)
+struct acpi_i2c_lookup {
+	struct i2c_board_info *info;
+	acpi_handle adapter_handle;
+	acpi_handle device_handle;
+};
+
+static int acpi_i2c_find_address(struct acpi_resource *ares, void *data)
 {
-	struct i2c_board_info *info = data;
+	struct acpi_i2c_lookup *lookup = data;
+	struct i2c_board_info *info = lookup->info;
+	struct acpi_resource_i2c_serialbus *sb;
+	acpi_handle adapter_handle;
+	acpi_status status;
 
-	if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS) {
-		struct acpi_resource_i2c_serialbus *sb;
+	if (info->addr || ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
+		return 1;
 
-		sb = &ares->data.i2c_serial_bus;
-		if (!info->addr && sb->type == ACPI_RESOURCE_SERIAL_TYPE_I2C) {
-			info->addr = sb->slave_address;
-			if (sb->access_mode == ACPI_I2C_10BIT_MODE)
-				info->flags |= I2C_CLIENT_TEN;
-		}
-	} else if (!info->irq) {
-		struct resource r;
+	sb = &ares->data.i2c_serial_bus;
+	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C)
+		return 1;
 
-		if (acpi_dev_resource_interrupt(ares, 0, &r))
-			info->irq = r.start;
+	/*
+	 * Extract the ResourceSource and make sure that the handle matches
+	 * with the I2C adapter handle.
+	 */
+	status = acpi_get_handle(lookup->device_handle,
+				 sb->resource_source.string_ptr,
+				 &adapter_handle);
+	if (ACPI_SUCCESS(status) && adapter_handle == lookup->adapter_handle) {
+		info->addr = sb->slave_address;
+		if (sb->access_mode == ACPI_I2C_10BIT_MODE)
+			info->flags |= I2C_CLIENT_TEN;
 	}
 
-	/* Tell the ACPI core to skip this resource */
 	return 1;
 }
 
@@ -128,6 +141,8 @@ static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
 {
 	struct i2c_adapter *adapter = data;
 	struct list_head resource_list;
+	struct acpi_i2c_lookup lookup;
+	struct resource_entry *entry;
 	struct i2c_board_info info;
 	struct acpi_device *adev;
 	int ret;
@@ -140,14 +155,37 @@ static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
 	memset(&info, 0, sizeof(info));
 	info.fwnode = acpi_fwnode_handle(adev);
 
+	memset(&lookup, 0, sizeof(lookup));
+	lookup.adapter_handle = ACPI_HANDLE(adapter->dev.parent);
+	lookup.device_handle = handle;
+	lookup.info = &info;
+
+	/*
+	 * Look up for I2cSerialBus resource with ResourceSource that
+	 * matches with this adapter.
+	 */
 	INIT_LIST_HEAD(&resource_list);
 	ret = acpi_dev_get_resources(adev, &resource_list,
-				     acpi_i2c_add_resource, &info);
+				     acpi_i2c_find_address, &lookup);
 	acpi_dev_free_resource_list(&resource_list);
 
 	if (ret < 0 || !info.addr)
 		return AE_OK;
 
+	/* Then fill IRQ number if any */
+	ret = acpi_dev_get_resources(adev, &resource_list, NULL, NULL);
+	if (ret < 0)
+		return AE_OK;
+
+	resource_list_for_each_entry(entry, &resource_list) {
+		if (resource_type(entry->res) == IORESOURCE_IRQ) {
+			info.irq = entry->res->start;
+			break;
+		}
+	}
+
+	acpi_dev_free_resource_list(&resource_list);
+
 	adev->power.flags.ignore_parent = true;
 	strlcpy(info.type, dev_name(&adev->dev), sizeof(info.type));
 	if (!i2c_new_device(adapter, &info)) {
@@ -160,6 +198,8 @@ static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
 	return AE_OK;
 }
 
+#define ACPI_I2C_MAX_SCAN_DEPTH 32
+
 /**
  * acpi_i2c_register_devices - enumerate I2C slave devices behind adapter
  * @adap: pointer to adapter
@@ -170,17 +210,13 @@ static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
  */
 static void acpi_i2c_register_devices(struct i2c_adapter *adap)
 {
-	acpi_handle handle;
 	acpi_status status;
 
-	if (!adap->dev.parent)
-		return;
-
-	handle = ACPI_HANDLE(adap->dev.parent);
-	if (!handle)
+	if (!adap->dev.parent || !has_acpi_companion(adap->dev.parent))
 		return;
 
-	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+				     ACPI_I2C_MAX_SCAN_DEPTH,
 				     acpi_i2c_add_device, NULL,
 				     adap, NULL);
 	if (ACPI_FAILURE(status))