1 // SPDX-License-Identifier: GPL-2.0+
3 * Serial core port device driver
5 * Copyright (C) 2023 Texas Instruments Incorporated - https://www.ti.com/
6 * Author: Tony Lindgren <tony@atomide.com>
9 #include <linux/device.h>
10 #include <linux/module.h>
11 #include <linux/pm_runtime.h>
12 #include <linux/serial_core.h>
13 #include <linux/spinlock.h>
15 #include "serial_base.h"
17 #define SERIAL_PORT_AUTOSUSPEND_DELAY_MS 500
19 /* Only considers pending TX for now. Caller must take care of locking */
20 static int __serial_port_busy(struct uart_port *port)
22 return !uart_tx_stopped(port) &&
23 uart_circ_chars_pending(&port->state->xmit);
26 static int serial_port_runtime_resume(struct device *dev)
28 struct serial_port_device *port_dev = to_serial_base_port_device(dev);
29 struct uart_port *port;
32 port = port_dev->port;
34 if (port->flags & UPF_DEAD)
37 /* Flush any pending TX for the port */
38 spin_lock_irqsave(&port->lock, flags);
39 if (__serial_port_busy(port))
40 port->ops->start_tx(port);
41 spin_unlock_irqrestore(&port->lock, flags);
44 pm_runtime_mark_last_busy(dev);
49 static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,
50 NULL, serial_port_runtime_resume, NULL);
52 static int serial_port_probe(struct device *dev)
54 pm_runtime_enable(dev);
55 pm_runtime_set_autosuspend_delay(dev, SERIAL_PORT_AUTOSUSPEND_DELAY_MS);
56 pm_runtime_use_autosuspend(dev);
61 static int serial_port_remove(struct device *dev)
63 pm_runtime_dont_use_autosuspend(dev);
64 pm_runtime_disable(dev);
70 * Serial core port device init functions. Note that the physical serial
71 * port device driver may not have completed probe at this point.
73 int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
75 return serial_ctrl_register_port(drv, port);
77 EXPORT_SYMBOL(uart_add_one_port);
79 void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
81 serial_ctrl_unregister_port(drv, port);
83 EXPORT_SYMBOL(uart_remove_one_port);
85 static struct device_driver serial_port_driver = {
87 .suppress_bind_attrs = true,
88 .probe = serial_port_probe,
89 .remove = serial_port_remove,
90 .pm = pm_ptr(&serial_port_pm),
93 int serial_base_port_init(void)
95 return serial_base_driver_register(&serial_port_driver);
98 void serial_base_port_exit(void)
100 serial_base_driver_unregister(&serial_port_driver);
103 MODULE_AUTHOR("Tony Lindgren <tony@atomide.com>");
104 MODULE_DESCRIPTION("Serial controller port driver");
105 MODULE_LICENSE("GPL");