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43066e3222
We accidently met the issue that the bash prompt is not shown after the
previous command done and until the next input if there's only one CPU
(In our issue other CPUs are isolated by isolcpus=). Further analysis
shows it's because the port entering runtime suspend even if there's
still pending chars in the buffer and the pending chars will only be
processed in next device resuming. We are using amba-pl011 and the
problematic flow is like below:
Bash kworker
tty_write()
file_tty_write()
n_tty_write()
uart_write()
__uart_start()
pm_runtime_get() // wakeup waker
queue_work()
pm_runtime_work()
rpm_resume()
status = RPM_RESUMING
serial_port_runtime_resume()
port->ops->start_tx()
pl011_tx_chars()
uart_write_wakeup()
[…]
__uart_start()
pm_runtime_get() < 0 // because runtime status = RPM_RESUMING
// later data are not commit to the port driver
status = RPM_ACTIVE
rpm_idle() -> rpm_suspend()
This patch tries to fix this by checking the port busy before entering
runtime suspending. A runtime_suspend callback is added for the port
driver. When entering runtime suspend the callback is invoked, if there's
still pending chars in the buffer then flush the buffer.
Fixes: 84a9582fd2 ("serial: core: Start managing serial controllers to enable runtime PM")
Cc: stable <stable@kernel.org>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240226152351.40924-1-yangyicong@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
128 lines
2.9 KiB
C
128 lines
2.9 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Serial core port device driver
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*
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* Copyright (C) 2023 Texas Instruments Incorporated - https://www.ti.com/
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* Author: Tony Lindgren <tony@atomide.com>
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*/
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#include <linux/device.h>
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#include <linux/module.h>
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#include <linux/pm_runtime.h>
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#include <linux/serial_core.h>
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#include <linux/spinlock.h>
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#include "serial_base.h"
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#define SERIAL_PORT_AUTOSUSPEND_DELAY_MS 500
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/* Only considers pending TX for now. Caller must take care of locking */
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static int __serial_port_busy(struct uart_port *port)
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{
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return !uart_tx_stopped(port) &&
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uart_circ_chars_pending(&port->state->xmit);
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}
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static int serial_port_runtime_resume(struct device *dev)
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{
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struct serial_port_device *port_dev = to_serial_base_port_device(dev);
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struct uart_port *port;
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unsigned long flags;
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port = port_dev->port;
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if (port->flags & UPF_DEAD)
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goto out;
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/* Flush any pending TX for the port */
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uart_port_lock_irqsave(port, &flags);
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if (__serial_port_busy(port))
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port->ops->start_tx(port);
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uart_port_unlock_irqrestore(port, flags);
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out:
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pm_runtime_mark_last_busy(dev);
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return 0;
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}
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static int serial_port_runtime_suspend(struct device *dev)
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{
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struct serial_port_device *port_dev = to_serial_base_port_device(dev);
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struct uart_port *port = port_dev->port;
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unsigned long flags;
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bool busy;
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if (port->flags & UPF_DEAD)
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return 0;
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uart_port_lock_irqsave(port, &flags);
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busy = __serial_port_busy(port);
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if (busy)
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port->ops->start_tx(port);
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uart_port_unlock_irqrestore(port, flags);
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if (busy)
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pm_runtime_mark_last_busy(dev);
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return busy ? -EBUSY : 0;
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}
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static DEFINE_RUNTIME_DEV_PM_OPS(serial_port_pm,
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serial_port_runtime_suspend,
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serial_port_runtime_resume, NULL);
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static int serial_port_probe(struct device *dev)
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{
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pm_runtime_enable(dev);
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pm_runtime_set_autosuspend_delay(dev, SERIAL_PORT_AUTOSUSPEND_DELAY_MS);
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pm_runtime_use_autosuspend(dev);
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return 0;
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}
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static int serial_port_remove(struct device *dev)
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{
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pm_runtime_dont_use_autosuspend(dev);
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pm_runtime_disable(dev);
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return 0;
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}
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/*
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* Serial core port device init functions. Note that the physical serial
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* port device driver may not have completed probe at this point.
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*/
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int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
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{
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return serial_ctrl_register_port(drv, port);
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}
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EXPORT_SYMBOL(uart_add_one_port);
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void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
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{
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serial_ctrl_unregister_port(drv, port);
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}
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EXPORT_SYMBOL(uart_remove_one_port);
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static struct device_driver serial_port_driver = {
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.name = "port",
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.suppress_bind_attrs = true,
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.probe = serial_port_probe,
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.remove = serial_port_remove,
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.pm = pm_ptr(&serial_port_pm),
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};
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int serial_base_port_init(void)
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{
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return serial_base_driver_register(&serial_port_driver);
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}
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void serial_base_port_exit(void)
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{
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serial_base_driver_unregister(&serial_port_driver);
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}
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MODULE_AUTHOR("Tony Lindgren <tony@atomide.com>");
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MODULE_DESCRIPTION("Serial controller port driver");
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MODULE_LICENSE("GPL");
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