Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 083/221] drm/i915: dont disable disconnected outputs | Date | Tue, 15 Jan 2013 10:50:10 -0800 |
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3.7-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Vetter <daniel.vetter@ffwll.ch>
commit b0a2658acb5bf9ca86b4aab011b7106de3af0add upstream.
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 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/gpu/drm/i915/intel_display.c | 4 ---- 1 file changed, 4 deletions(-)
--- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -7298,10 +7298,6 @@ intel_modeset_stage_output_state(struct 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. */
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