makes sense Reviewed-by: Rodrigo Vivi <rodrigo.vivi at gmail.com> couldn't we close the bug already? On Tue, Dec 18, 2012 at 6:37 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote: > This piece of neat lore has been ported painstakingly and bug-for-bug > compatible from the old crtc helper code. > > Imo it's utter nonsense. > > If you disconnected a cable and before you reconnect it, userspace (or > the kernel) does an set_crtc call, this will result in that connector > getting disabled. Which will result in a nice black screen when > plugging in the cable again. > > There's absolutely no reason the kernel does such policy enforcements > - if userspace tries to set up a mode on something disconnected we > might fail loudly (since the dp link training fails), but silently > adjusting the output configuration behind userspace's back is a recipe > for disaster. Specifically I think that this could explain some of our > MI_WAIT hangs around suspend, where userspace issues a scanline wait > on a disable pipe. This mechanisims here could explain how that pipe > got disabled without userspace noticing. > > Note that this fixes a NULL deref at BIOS takeover when the firmware > sets up a disconnected output in a clone configuration with a > connected output on the 2nd pipe: When doing the full modeset we don't > have a mode for the 2nd pipe and OOPS. On the first pipe this doesn't > matter, since at boot-up the fbdev helpers will set up the choosen > configuration on that on first. Since this is now the umptenth bug > around handling this imo brain-dead semantics correctly, I think it's > time to kill it and see whether there's any userspace out there which > relies on this. > > It also nicely demonstrates that we have a tiny window where DP > hotplug can still kill the driver. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=58396 > Cc: stable at vger.kernel.org > Tested-by: Peter Ujfalusi <peter.ujfalusi at gmail.com> > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> > --- > drivers/gpu/drm/i915/intel_display.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > index 34832bc0..399f862 100644 > --- a/drivers/gpu/drm/i915/intel_display.c > +++ b/drivers/gpu/drm/i915/intel_display.c > @@ -7632,10 +7632,6 @@ intel_modeset_stage_output_state(struct drm_device *dev, > DRM_DEBUG_KMS("encoder changed, full mode switch\n"); > config->mode_changed = true; > } > - > - /* Disable all disconnected encoders. */ > - if (connector->base.status == connector_status_disconnected) > - connector->new_encoder = NULL; > } > /* connector->new_encoder is now updated for all connectors. */ > > -- > 1.7.11.7 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx at lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Rodrigo Vivi Blog: http://blog.vivi.eng.br
