1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Serial core port device driver
4 *
5 * Copyright (C) 2023 Texas Instruments Incorporated - https://www.ti.com/
6 * Author: Tony Lindgren <tony@atomide.com>
7 */
8
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>
14
15#include "serial_base.h"
16
17#define SERIAL_PORT_AUTOSUSPEND_DELAY_MS	500
18
19/* Only considers pending TX for now. Caller must take care of locking */
20static int __serial_port_busy(struct uart_port *port)
21{
22	return !uart_tx_stopped(port) &&
23		uart_circ_chars_pending(&port->state->xmit);
24}
25
26static int serial_port_runtime_resume(struct device *dev)
27{
28	struct serial_port_device *port_dev = to_serial_base_port_device(dev);
29	struct uart_port *port;
30	unsigned long flags;
31
32	port = port_dev->port;
33
34	if (port->flags & UPF_DEAD)
35		goto out;
36
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);
42
43out:
44	pm_runtime_mark_last_busy(dev);
45
46	return 0;
47}
48
49static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,
50				 NULL, serial_port_runtime_resume, NULL);
51
52static int serial_port_probe(struct device *dev)
53{
54	pm_runtime_enable(dev);
55	pm_runtime_set_autosuspend_delay(dev, SERIAL_PORT_AUTOSUSPEND_DELAY_MS);
56	pm_runtime_use_autosuspend(dev);
57
58	return 0;
59}
60
61static int serial_port_remove(struct device *dev)
62{
63	pm_runtime_dont_use_autosuspend(dev);
64	pm_runtime_disable(dev);
65
66	return 0;
67}
68
69/*
70 * Serial core port device init functions. Note that the physical serial
71 * port device driver may not have completed probe at this point.
72 */
73int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
74{
75	return serial_ctrl_register_port(drv, port);
76}
77EXPORT_SYMBOL(uart_add_one_port);
78
79void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
80{
81	serial_ctrl_unregister_port(drv, port);
82}
83EXPORT_SYMBOL(uart_remove_one_port);
84
85static struct device_driver serial_port_driver = {
86	.name = "port",
87	.suppress_bind_attrs = true,
88	.probe = serial_port_probe,
89	.remove = serial_port_remove,
90	.pm = pm_ptr(&serial_port_pm),
91};
92
93int serial_base_port_init(void)
94{
95	return serial_base_driver_register(&serial_port_driver);
96}
97
98void serial_base_port_exit(void)
99{
100	serial_base_driver_unregister(&serial_port_driver);
101}
102
103MODULE_AUTHOR("Tony Lindgren <tony@atomide.com>");
104MODULE_DESCRIPTION("Serial controller port driver");
105MODULE_LICENSE("GPL");
106