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authorDaniel Vetter <daniel.vetter@ffwll.ch>2012-12-18 09:37:54 +0100
committerDaniel Vetter <daniel.vetter@ffwll.ch>2012-12-18 21:32:56 +0100
commitb0a2658acb5bf9ca86b4aab011b7106de3af0add (patch)
parentb45305fce5bb1abec263fcff9d81ebecd6306ede (diff)
drm/i915: don't disable disconnected outputs
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@vger.kernel.org Tested-by: Peter Ujfalusi <peter.ujfalusi@gmail.com> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 files changed, 0 insertions, 4 deletions
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 82267b27b8f6..bc0b7aa0ab96 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8133,10 +8133,6 @@ 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. */