Re: Bisects that are neither good nor bad

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > With the resume failure I'm seeing, we don't get back to userspace
> > > to run anything like this. It goes bang long before that.
> > > 
> > > The SATA fix Mark proposed also didn't improve the situation for me :-/
> > 
> > If setserial -a is needed.. it means that someone really needs to fix
> > suspend/resume support for serial... do it on working machine to
> > enable debugging of broken ones...
> 
> I've explained why this occurs in bugzilla - but for the sake of
> repeating repeating repeating myself at great length, let's repeat
> it again here.
> 
> The serial layer does _not_ have access to the "current" termios
> settings due to the layering by the tty subsystem.  If the serial
> port being used by serial console has been opened once by the user,
> but is closed at the moment when a suspend/resume cycle occurs,
> the serial layer and lower level drivers do not have access to the
> baud rate.

Could serial layer just cache "last baud rate" in some kind of
software shadow register? Yes, it is slightly ugly, but should do the trick.

> Hence, it is impossible for the serial layer to do a proper resume
> in this scenario.  Either always suspend with the console port open
> or never open the console port before suspend.  Alternatively, we
> need the tty layer to mature, so that there is some way for drivers
> to get the termios structures for the console from the upper layer.
> Or maybe we need the tty layer to be responsible for implementing
> suspend/resume support for tty devices.

								Pavel

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