Comment 12 for bug 1205263

> * If it's safe to turn on power saving on battery mode after 1 (or 10,
> as in above suggestion) seconds, why isn't it safe to do it on AC as
> well? Are there some drawbacks like a long wakeup time, or anything else
> which causes a noticeable regression in that mode? Or is that still the
> potential click/pop problem as pointed out in
> http://www.mjmwired.net/kernel/Documentation/sound/alsa/powersave.txt ?

Well, all of that has happened in the past - most commonly pop/clicks, wakeup times (hardly more than a few 100 ms though), and in worst case, controller or codec wakeup failure (leading to no audio at all).
The vast majority of these problems have been resolved (seen over a five year period or so), but it's difficult to know how many problems remain.

However, most laptops have been on battery, so I assume the issues there have been resolved to a very large degree. Desktop machines are always AC connected, so it's more risky for those. I'd say that at least for laptops, I'd vote for taking the risk. For desktops, not so sure.

> * We don't want click/pop noises on battery either. Are we actually
> aware of that happening, from bug reports etc? It seems to me that we
> should enable audio power saving on hardware where it's safe to do so,
> not depending on battery mode.

Click/pop noises are not commonly reported today, but it happens. However, I kind of understand the intention too - given non-perfect drivers, on battery you might prefer having a few extra minutes of battery and live with the pop, whereas on AC, you don't have to make that consideration.

> * Thirdly, above documentation actually suggests that "1" is a bad
> default, so in the powersaving case we should change that to 10.

PulseAudio keeps the device open for 5 seconds after the last client has stopped accessing the sound card, so even if set to "1", it's 5+1 = 6 seconds for the most common use cases. However, 5 here seems to be a reasonable compromise, then we end up with 5+5 = 10.