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serial-core: resume serial hardware with no_console_suspend

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Perform a tricky suspend/resume even with no_console_suspend.

With no_console_suspend, kernel skips serial port suspend/resume and the
serial hardware may remain in undefined state after resume. It actually
happens on devices that don't have BIOS that handle serial
initialization. It makes impossible to use serial console after resume.

Devices affected by this problem include:
Sharp Zaurus devices
Several PXA based ARM embedded boards

The patch does:
- Save the hardware state
- Perform buffer flush in time of its suspend call
- Tell the driver that port is suspended
- But still accept new data
- And keep console hardware in state that allows to send them

It allows to capture late console messages without breaking console
after resume.

This is just a resend of a patch discussed in these threads, as the
patch was not yet applied.

"Possible suspend/resume regression in .32-rc?" (Nov 1-5, 2009, ARM
list, later LKML)

"serial-core: resume serial hardware with no_console_suspend" (Sep
15-Oct 18, 2009, LKML & ARM lists)

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
Tested-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Tested-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Stanislav Brabec 2009-12-02 16:20:56 +01:00 committed by Greg Kroah-Hartman
parent 6d34855d9a
commit 4547be7809
1 changed files with 33 additions and 55 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

88
drivers/serial/serial_core.c
View File

@ -2006,12 +2006,6 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
mutex_lock(&port->mutex);
if (!console_suspend_enabled && uart_console(uport)) {
/* we're going to avoid suspending serial console */
mutex_unlock(&port->mutex);
return 0;
}
tty_dev = device_find_child(uport->dev, &match, serial_match_port);
if (device_may_wakeup(tty_dev)) {
enable_irq_wake(uport->irq);
@ -2019,20 +2013,23 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
mutex_unlock(&port->mutex);
return 0;
}
uport->suspended = 1;
if (console_suspend_enabled || !uart_console(uport))
uport->suspended = 1;
if (port->flags & ASYNC_INITIALIZED) {
const struct uart_ops *ops = uport->ops;
int tries;
set_bit(ASYNCB_SUSPENDED, &port->flags);
clear_bit(ASYNCB_INITIALIZED, &port->flags);
if (console_suspend_enabled || !uart_console(uport)) {
set_bit(ASYNCB_SUSPENDED, &port->flags);
clear_bit(ASYNCB_INITIALIZED, &port->flags);
spin_lock_irq(&uport->lock);
ops->stop_tx(uport);
ops->set_mctrl(uport, 0);
ops->stop_rx(uport);
spin_unlock_irq(&uport->lock);
spin_lock_irq(&uport->lock);
ops->stop_tx(uport);
ops->set_mctrl(uport, 0);
ops->stop_rx(uport);
spin_unlock_irq(&uport->lock);
}
/*
* Wait for the transmitter to empty.
@ -2047,16 +2044,18 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
drv->dev_name,
drv->tty_driver->name_base + uport->line);
ops->shutdown(uport);
if (console_suspend_enabled || !uart_console(uport))
ops->shutdown(uport);
}
/*
* Disable the console device before suspending.
*/
if (uart_console(uport))
if (console_suspend_enabled && uart_console(uport))
console_stop(uport->cons);
uart_change_pm(state, 3);
if (console_suspend_enabled || !uart_console(uport))
uart_change_pm(state, 3);
mutex_unlock(&port->mutex);
@ -2073,29 +2072,6 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
mutex_lock(&port->mutex);
if (!console_suspend_enabled && uart_console(uport)) {
/* no need to resume serial console, it wasn't suspended */
/*
* First try to use the console cflag setting.
*/
memset(&termios, 0, sizeof(struct ktermios));
termios.c_cflag = uport->cons->cflag;
/*
* If that's unset, use the tty termios setting.
*/
if (termios.c_cflag == 0)
termios = *state->port.tty->termios;
else {
termios.c_ispeed = termios.c_ospeed =
tty_termios_input_baud_rate(&termios);
termios.c_ispeed = termios.c_ospeed =
tty_termios_baud_rate(&termios);
}
uport->ops->set_termios(uport, &termios, NULL);
mutex_unlock(&port->mutex);
return 0;
}
tty_dev = device_find_child(uport->dev, &match, serial_match_port);
if (!uport->suspended && device_may_wakeup(tty_dev)) {
disable_irq_wake(uport->irq);
@ -2121,21 +2097,23 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
spin_lock_irq(&uport->lock);
ops->set_mctrl(uport, 0);
spin_unlock_irq(&uport->lock);
ret = ops->startup(uport);
if (ret == 0) {
uart_change_speed(state, NULL);
spin_lock_irq(&uport->lock);
ops->set_mctrl(uport, uport->mctrl);
ops->start_tx(uport);
spin_unlock_irq(&uport->lock);
set_bit(ASYNCB_INITIALIZED, &port->flags);
} else {
/*
* Failed to resume - maybe hardware went away?
* Clear the "initialized" flag so we won't try
* to call the low level drivers shutdown method.
*/
uart_shutdown(state);
if (console_suspend_enabled || !uart_console(uport)) {
ret = ops->startup(uport);
if (ret == 0) {
uart_change_speed(state, NULL);
spin_lock_irq(&uport->lock);
ops->set_mctrl(uport, uport->mctrl);
ops->start_tx(uport);
spin_unlock_irq(&uport->lock);
set_bit(ASYNCB_INITIALIZED, &port->flags);
} else {
/*
* Failed to resume - maybe hardware went away?
* Clear the "initialized" flag so we won't try
* to call the low level drivers shutdown method.
*/
uart_shutdown(state);
}
}
clear_bit(ASYNCB_SUSPENDED, &port->flags);