drivers/tty/serial/serial_port.c

   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 */
  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
  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
  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
  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  */
  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
  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
  93 int serial_base_port_init(void)
  94 {
  95         return serial_base_driver_register(&serial_port_driver);
  96 }
  97
  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");