RE: [PATCH] lan78xx: Protect runtime_auto check by #ifdef CONFIG_PM

[Alan Stern]

On Mon, 21 Mar 2016 Woojung.Huh@xxxxxxxxxxxxx wrote:

> > But this leaves open the issue that querying the device too often will
> > prevent it from going into autosuspend.  It seems to me that the best
> > way to deal with this is to make sure that the autosuspend timeout is
> > shorter than the interal between queries, not to make the querying
> > conditional on !runtime_auto.
> 
> Short autosuspend timeout can affect performance. For instance our experiments showed that
> shorter than 10sec timeout made Ethernet performance degrade because of wakeup delays.
> So, just putting shorter timeout may have some side effects.

Sure.  This just means that you need a long statistics interval --
longer than the autosuspend timeout.  That's why I suggested making the
interval adjustable.

Alternatively, you could automatically set the statistics interval to
the autosuspend timeout (or 0 if autosuspend is disabled) plus some
fixed value.

Alan Stern