Re: [PATCH: 2/2] [SERIAL] avoid stalling suspend if serial port won't drain

[Pavel Machek <pavel@ucw.cz>]

On Mon 2008-01-14 00:29:12, Russell King wrote:
> On Fri, Jan 11, 2008 at 10:17:21AM +0000, Pavel Machek wrote:
> > On Tue 2008-01-08 11:57:03, Russell King wrote:
> > > +		if (!tries)
> > > +			printk(KERN_ERR "%s%s%s%d: Unable to drain transmitter\n",
> > > +			       port->dev ? port->dev->bus_id : "",
> > > +			       port->dev ? ": " : "",
> > > +			       drv->dev_name, port->line);
> > >  
> > >  		ops->shutdown(port);
> > >  	}
> > > 
> > 
> > Is printk() enough for 'we've just lost your data' condition? Maybe we
> > should abort suspend if we can't drain fifo?
> 
> That would mean that a port set for hardware flow control, with hardware
> implemented flow control, has CTS deasserted, you'll never suspend.

Yep. 

> If you're suspending because your battery is almost dead what would you
> prefer - the system being prevented from suspending and losing complete
> power unexpectedly, resulting in complete data loss, or losing the
> characters in the serial port and suspending?
> 
> Which is the lesser of two evils?

Not sure, but there's third option -- correct but more work. What
about saving/restoring fifo state? That will not stall suspend, nor
will loose data.
								Pavel
-- 
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