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 */
__serial_port_busy(struct uart_port * port)20 static 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
serial_port_runtime_resume(struct device * dev)26 static 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
43 out:
44 pm_runtime_mark_last_busy(dev);
45
46 return 0;
47 }
48
49 static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,
50 NULL, serial_port_runtime_resume, NULL);
51
serial_port_probe(struct device * dev)52 static 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
serial_port_remove(struct device * dev)61 static 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 */
uart_add_one_port(struct uart_driver * drv,struct uart_port * port)73 int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
74 {
75 return serial_ctrl_register_port(drv, port);
76 }
77 EXPORT_SYMBOL(uart_add_one_port);
78
uart_remove_one_port(struct uart_driver * drv,struct uart_port * port)79 void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
80 {
81 serial_ctrl_unregister_port(drv, port);
82 }
83 EXPORT_SYMBOL(uart_remove_one_port);
84
85 static 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
serial_base_port_init(void)93 int serial_base_port_init(void)
94 {
95 return serial_base_driver_register(&serial_port_driver);
96 }
97
serial_base_port_exit(void)98 void serial_base_port_exit(void)
99 {
100 serial_base_driver_unregister(&serial_port_driver);
101 }
102
103 MODULE_AUTHOR("Tony Lindgren <tony@atomide.com>");
104 MODULE_DESCRIPTION("Serial controller port driver");
105 MODULE_LICENSE("GPL");
106