Re: [PATCH 4/6] drm/i915: enable VT switchless resume v2

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Mon, 18 Mar 2013 19:50:37 +0100
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Mon, Mar 18, 2013 at 6:42 PM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> > On Mon, 18 Mar 2013 08:49:07 +0100
> > Daniel Vetter <daniel@ffwll.ch> wrote:
> >
> >> On Tue, Feb 19, 2013 at 12:11:41PM -0800, Jesse Barnes wrote:
> >> > With the other bits in place, we can do this safely.
> >> >
> >> > v2: disable backlight on suspend to prevent premature enablement on resume
> >> >
> >> > Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> >> > ---
> >> >  drivers/gpu/drm/i915/i915_drv.c |   12 +++++++++---
> >> >  drivers/gpu/drm/i915/intel_fb.c |    3 +++
> >> >  2 files changed, 12 insertions(+), 3 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> >> > index c5b8c81..e76b038 100644
> >> > --- a/drivers/gpu/drm/i915/i915_drv.c
> >> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> >> > @@ -492,9 +492,10 @@ static int i915_drm_freeze(struct drm_device *dev)
> >> >
> >> >             cancel_delayed_work_sync(&dev_priv->rps.delayed_resume_work);
> >> >
> >> > -           intel_modeset_disable(dev);
> >>
> >> As discussed in person last week, simply dropping this will probably kill
> >> S0i3 support.
> >
> > Not really, since DPMS will be off in that case too generally, but it
> > does make testing harder.
> 
> Hm, where do we do that currently? Without fbcon I don't see it, and
> we can't really rely on userspace to get this right I guess ...

I was assuming userspace would do it, but yes we shouldn't require that.

> > I think it just needs to be a low level call to crtc disable on each
> > pipe, otherwise we'll zap the state we're trying to save.
> 
> That just reminded me that we also should restore the right dpms state
> I think. At least I'm not too sure whether we'll currently do that
> (and whether the modeset state tracker would catch it). Otoh dpms
> standby/suspend died with gen4 ;-)

Hm yeah haven't tested that at all.  One typical kind of suspend will
happen after DPMS off when the machine has been idle for some period.
When it comes back up the user will probably want to see the display.
But we don't have to enforce that on the kernel side; we can leave it
to userspace.

-- 
Jesse Barnes, Intel Open Source Technology Center