serial: core: Move tty and serdev to be children of serial core port device

Let's move tty and serdev controller to be children of the serial core port
device. This way the runtime PM usage count of a child device propagates
to the serial hardware device.

The tty and serdev devices are associated with a specific serial port of
a serial hardware controller device, and we now have serial core hierarchy
of controllers and ports.

The tty device moves happily with just a change of the parent device and
update of device_find_child() handling. The serdev device init needs some
changes to separate the serial hardware controller device from the parent
device.

With this change the tty devices move under sysfs similar to this x86_64
qemu example of a diff of "find /sys -name ttyS*":

 /sys/class/tty/ttyS0
 /sys/class/tty/ttyS3
 /sys/class/tty/ttyS1
-/sys/devices/pnp0/00:04/tty/ttyS0
-/sys/devices/platform/serial8250/tty/ttyS2
-/sys/devices/platform/serial8250/tty/ttyS3
-/sys/devices/platform/serial8250/tty/ttyS1
+/sys/devices/pnp0/00:04/00:04:0/00:04:0.0/tty/ttyS0
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.3/tty/ttyS3
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.1/tty/ttyS1
+/sys/devices/platform/serial8250/serial8250:0/serial8250:0.2/tty/ttyS2

If a serdev device is used instead of a tty, it moves in a similar way.

Suggested-by: Johan Hovold <johan@kernel.org>
Cc: Maximilian Luz <luzmaximilian@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20231113080758.30346-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index a5fdaf5e148e..3090e3454c44 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -468,6 +468,7 @@ EXPORT_SYMBOL_GPL(serdev_device_alloc);
 
 /**
  * serdev_controller_alloc() - Allocate a new serdev controller
+ * @host:	serial port hardware controller device
  * @parent:	parent device
  * @size:	size of private data
  *
@@ -476,8 +477,9 @@ EXPORT_SYMBOL_GPL(serdev_device_alloc);
  * The allocated private data region may be accessed via
  * serdev_controller_get_drvdata()
  */
-struct serdev_controller *serdev_controller_alloc(struct device *parent,
-					      size_t size)
+struct serdev_controller *serdev_controller_alloc(struct device *host,
+						  struct device *parent,
+						  size_t size)
 {
 	struct serdev_controller *ctrl;
 	int id;
@@ -502,7 +504,8 @@ struct serdev_controller *serdev_controller_alloc(struct device *parent,
 	ctrl->dev.type = &serdev_ctrl_type;
 	ctrl->dev.bus = &serdev_bus_type;
 	ctrl->dev.parent = parent;
-	device_set_node(&ctrl->dev, dev_fwnode(parent));
+	ctrl->host = host;
+	device_set_node(&ctrl->dev, dev_fwnode(host));
 	serdev_controller_set_drvdata(ctrl, &ctrl[1]);
 
 	dev_set_name(&ctrl->dev, "serial%d", id);
@@ -665,7 +668,7 @@ static int acpi_serdev_check_resources(struct serdev_controller *ctrl,
 		acpi_get_parent(adev->handle, &lookup.controller_handle);
 
 	/* Make sure controller and ResourceSource handle match */
-	if (!device_match_acpi_handle(ctrl->dev.parent, lookup.controller_handle))
+	if (!device_match_acpi_handle(ctrl->host, lookup.controller_handle))
 		return -ENODEV;
 
 	return 0;
@@ -730,7 +733,7 @@ static int acpi_serdev_register_devices(struct serdev_controller *ctrl)
 	bool skip;
 	int ret;
 
-	if (!has_acpi_companion(ctrl->dev.parent))
+	if (!has_acpi_companion(ctrl->host))
 		return -ENODEV;
 
 	/*
@@ -739,7 +742,7 @@ static int acpi_serdev_register_devices(struct serdev_controller *ctrl)
 	 * succeed in this case, so that the proper serdev devices can be
 	 * added "manually" later.
 	 */
-	ret = acpi_quirk_skip_serdev_enumeration(ctrl->dev.parent, &skip);
+	ret = acpi_quirk_skip_serdev_enumeration(ctrl->host, &skip);
 	if (ret)
 		return ret;
 	if (skip)