RE: Subtle semantic issue with sleep callbacks in drivers

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2003-04-16 at 20:39, Patrick Mochel wrote:

> I completely agree with Andy. We should not re-POST the video hardware, no
> matter what. The idea behind ACPI is that the OS takes care of everything, 
> including video save/restore. 

If I understand Alan properly, we don't always have choice, some BIOSes
will do it anyway...

> We may not have the documentation to properly do that for all hardware 
> currently, but that is something that we have to suck up and deal with. 
> For now, we go with hardware that we're able to handle. 
> 
> The drivers that cannot support reinitialization will not be able to 
> support suspend-to-RAM. When we get to a point where it really becomes an 
> issue (i.e. after we have decent working code), then we concentrate on 
> getting the appropriate docuementation (or code itself, source or binary) 
> to do it correctly. 

It is now already ! I don't think we will _ever_ get ATI and nVidia
provide enough documentation to POST all chip models (which isn't always
possible without knowledge of every single way the chip is wired on a
each board).

Currently, I cannot implement suspend-to-RAM on the latest PowerBooks
because of that (they use nVidia chip that are powered down and not just
unclocked unlike earlier ATI based models) because of that. Nor can I
implement it on any other "desktop" Mac.

> Trying to figure out if we need to POST or not for different hardware, 
> based what the driver knows, is going to become quite a mess real fast. I 
> don't want to deal with the pain, and would rather take the high ground, 
> even if it means suffering in the short term. 

When I finally have an implementation of an OF runtime so I can re-POST
the card, I could eventually have the driver itself call this to explicitely
ask for a re-POST...

Ben.