[Intel-gfx] [PATCH 3/4] drm/i915: enable VT switchless resume v3

[Chris Wilson]

On Fri, May 16, 2014 at 11:38:07PM +0100, Chris Wilson wrote:
> On Fri, May 16, 2014 at 03:20:47PM -0700, Jesse Barnes wrote:
> > On Mon, 21 Apr 2014 18:37:31 +0200
> > Knut Petersen <Knut_Petersen at t-online.de> wrote:
> > > > +	/* This driver doesn't need a VT switch to restore the mode on resume */
> > > > +	info->skip_vt_switch = true;
> > > > +
> > > >   	drm_fb_helper_fill_fix(info, fb->pitches[0], fb->depth);
> > > >   	drm_fb_helper_fill_var(info, &ifbdev->helper, sizes->fb_width, sizes->fb_height);
> > 
> > Is it sufficient to just revert this part?  Or are the other bits
> > needed too?
> > 
> > Sorry for the delay on this, I've been traveling a lot the past month
> > and buried in other stuff so out of touch with much of my email.
> 
> The key step here is that X is restarted after resume. The slow down was
> due to X not finding any connected outputs and so disabling them all,
> setting up a dummy 1024x768 fb which really confused KDE. (KDE queries
> the config causing a forced reprobe of all outputs, setups the display
> for the native 1280x1024, but screws up KDE's own bookkeeping.)
> 
> The impact has been fixed by handling the connector->status more
> robusting during initial output probing in X. What remains is the
> question whether connector->status can be set appropriately upon resume?
> It requires a detection cycle to be sure that the outputs are still
> there, which is arguably better deferred to userspace. To be consistent
> the BIOS take over code should mark connector->status as unknown for the
> CRTCs it takes over without doing a detection cycle (where we just
> presume that the CRTC/output being enabled means something is on the
> other end of the pipe and is still valid).

Hmm. Why didn't fbcon respond to the hotplug event on resume and perform
a detection cycle before Knut was able to type startx on the console?
That I think is the bug.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre