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 uart_port_lock_irqsave(port, &flags);
39 if (__serial_port_busy(port))
40 port->ops->start_tx(port);
41 uart_port_unlock_irqrestore(port, flags);
44 pm_runtime_mark_last_busy(dev);
49 static int serial_port_runtime_suspend(struct device *dev)
51 struct serial_port_device *port_dev = to_serial_base_port_device(dev);
52 struct uart_port *port = port_dev->port;
56 if (port->flags & UPF_DEAD)
59 uart_port_lock_irqsave(port, &flags);
60 busy = __serial_port_busy(port);
62 port->ops->start_tx(port);
63 uart_port_unlock_irqrestore(port, flags);
66 pm_runtime_mark_last_busy(dev);
68 return busy ? -EBUSY : 0;
71 static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,
72 serial_port_runtime_suspend,
73 serial_port_runtime_resume, NULL);
75 static int serial_port_probe(struct device *dev)
77 pm_runtime_enable(dev);
78 pm_runtime_set_autosuspend_delay(dev, SERIAL_PORT_AUTOSUSPEND_DELAY_MS);
79 pm_runtime_use_autosuspend(dev);
84 static int serial_port_remove(struct device *dev)
86 pm_runtime_dont_use_autosuspend(dev);
87 pm_runtime_disable(dev);
93 * Serial core port device init functions. Note that the physical serial
94 * port device driver may not have completed probe at this point.
96 int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
98 return serial_ctrl_register_port(drv, port);
100 EXPORT_SYMBOL(uart_add_one_port);
102 void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
104 serial_ctrl_unregister_port(drv, port);
106 EXPORT_SYMBOL(uart_remove_one_port);
108 static struct device_driver serial_port_driver = {
110 .suppress_bind_attrs = true,
111 .probe = serial_port_probe,
112 .remove = serial_port_remove,
113 .pm = pm_ptr(&serial_port_pm),
116 int serial_base_port_init(void)
118 return serial_base_driver_register(&serial_port_driver);
121 void serial_base_port_exit(void)
123 serial_base_driver_unregister(&serial_port_driver);
126 MODULE_AUTHOR("Tony Lindgren <tony@atomide.com>");
127 MODULE_DESCRIPTION("Serial controller port driver");
128 MODULE_LICENSE("GPL");