[Intel-gfx] Doing restore by setting modes

[Jesse Barnes]

On Sat, 09 May 2009 15:10:00 -0700
Keith Packard <keithp at keithp.com> wrote:

> I'm having trouble with Display Port suspend/resume -- configuring the
> output is fairly tricky and depends on doing things in the right order
> at the right time. At this point, on resume, the display refuses to
> re-train, so you're left with a black screen. Setting the screen to a
> different mode and back to the preferred mode fixes it, unlike
> everything else I've tried (including turning it off and back on).
> 
> I'm wondering if we shouldn't just bail on much of the suspend/resume
> code and have resume just re-configure outputs using the existing
> output configuration code. Seems like that would result in less code
> and fewer inconsistencies between the resume and normal modeset paths.

Yeah, that's been on the TODO list for awhile now.  Though I think we
may need to keep the current code for non-KMS configs.

We'll also need to keep around a chunk of register save/restore for the
global, non-mode setting related state, but that should be fairly small
compared to all the mode stuff.

The KMS save/restore could probably be generic too; we just need to
save the current mode_config and re-apply it at resume time.

-- 
Jesse Barnes, Intel Open Source Technology Center