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Date: Thu, 3 Dec 2009 14:51:40 +0100
From: Daniel Mack <daniel@...aq.de>
To: Stanislav Brabec <sbrabec@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux@....linux.org.uk,
linux-kernel@...r.kernel.org, alan@...rguk.ukuu.org.uk,
gregkh@...e.de, Pavel Machek <pavel@....cz>, saxena@...top.org,
Eric Miao <eric.y.miao@...il.com>, s.hauer@...gutronix.de,
Haojian Zhuang <haojian.zhuang@...il.com>
Subject: Re: [PATCH]serial-core: resume serial hardware with
no_console_suspend (resend)
On Wed, Dec 02, 2009 at 04:20:56PM +0100, Stanislav Brabec wrote:
> 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
True, I had occasions where the serial console did not get back to life
after suspend on a PXA300 based device. It didn't always happen though.
> 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@...e.cz>
> Tested-by: Haojian Zhuang <haojian.zhuang@...il.com>
And I didn't see that problem anymore since your patch is applied,
great!
Tested-by: Daniel Mack <daniel@...aq.de>
Thanks,
Daniel
> diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
> index dcc7244..f1e1ab2 100644
> --- a/drivers/serial/serial_core.c
> +++ b/drivers/serial/serial_core.c
> @@ -2008,12 +2008,6 @@ 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);
> @@ -2021,20 +2015,23 @@ 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.
> @@ -2049,16 +2046,18 @@ 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);
>
> @@ -2075,29 +2074,6 @@ 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);
> @@ -2123,21 +2099,23 @@ 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);
>
>
> --
> Best Regards / S pozdravem,
>
> Stanislav Brabec
> software developer
> ---------------------------------------------------------------------
> SUSE LINUX, s. r. o. e-mail: sbrabec@...e.cz
> Lihovarská 1060/12 tel: +420 284 028 966, +49 911 740538747
> 190 00 Praha 9 fax: +420 284 028 951
> Czech Republic http://www.suse.cz/
>
>
>
>
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