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	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);
 42
 43out:
 44	pm_runtime_mark_last_busy(dev);
 45
 46	return 0;
 47}
 48
 49static int serial_port_runtime_suspend(struct device *dev)
 50{
 51	struct serial_port_device *port_dev = to_serial_base_port_device(dev);
 52	struct uart_port *port = port_dev->port;
 53	unsigned long flags;
 54	bool busy;
 55
 56	if (port->flags & UPF_DEAD)
 57		return 0;
 58
 59	uart_port_lock_irqsave(port, &flags);
 60	busy = __serial_port_busy(port);
 61	if (busy)
 62		port->ops->start_tx(port);
 63	uart_port_unlock_irqrestore(port, flags);
 64
 65	if (busy)
 66		pm_runtime_mark_last_busy(dev);
 67
 68	return busy ? -EBUSY : 0;
 69}
 70
 71static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,
 72				 serial_port_runtime_suspend,
 73				 serial_port_runtime_resume, NULL);
 74
 75static int serial_port_probe(struct device *dev)
 76{
 77	pm_runtime_enable(dev);
 78	pm_runtime_set_autosuspend_delay(dev, SERIAL_PORT_AUTOSUSPEND_DELAY_MS);
 79	pm_runtime_use_autosuspend(dev);
 80
 81	return 0;
 82}
 83
 84static int serial_port_remove(struct device *dev)
 85{
 86	pm_runtime_dont_use_autosuspend(dev);
 87	pm_runtime_disable(dev);
 88
 89	return 0;
 90}
 91
 92/*
 93 * Serial core port device init functions. Note that the physical serial
 94 * port device driver may not have completed probe at this point.
 95 */
 96int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
 97{
 98	return serial_ctrl_register_port(drv, port);
 99}
100EXPORT_SYMBOL(uart_add_one_port);
101
102void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
103{
104	serial_ctrl_unregister_port(drv, port);
105}
106EXPORT_SYMBOL(uart_remove_one_port);
107
108static struct device_driver serial_port_driver = {
109	.name = "port",
110	.suppress_bind_attrs = true,
111	.probe = serial_port_probe,
112	.remove = serial_port_remove,
113	.pm = pm_ptr(&serial_port_pm),
114};
115
116int serial_base_port_init(void)
117{
118	return serial_base_driver_register(&serial_port_driver);
119}
120
121void serial_base_port_exit(void)
122{
123	serial_base_driver_unregister(&serial_port_driver);
124}
125
126MODULE_AUTHOR("Tony Lindgren <tony@atomide.com>");
127MODULE_DESCRIPTION("Serial controller port driver");
128MODULE_LICENSE("GPL");