[RFC PATCH 3/4] tty: serial: 8250 core: add runtime pm

[One Thousand Gnomes]

On Fri,  4 Jul 2014 18:34:10 +0200
Sebastian Andrzej Siewior <bigeasy at linutronix.de> wrote:

> While comparing the OMAP-serial and the 8250 part of this I noticed that
> the the latter does not use runtime-pm.

Yes it does, but 8250 parts (generally - omap presumably is special
here ?) need to be powered on to transmit/receive not just for register
access. The core uart layer implements a "pm" operation for this.

As 8250_dw uses runtime pm to implement the pm operation it's not as
simple as assumign it won't get triggered.

I *think* this is ok because the designware and other cases would take a
reference on open and drop it on close, so avoiding any confusion, but
for the register accesses on a closed port it would benefit from a
further double check with Mika especially as the suspend/resume on the
LPSS block on some Intel devices is a little bit too "interesting" for
comfort.

Otherwise however I think this is good.

Alan