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author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2012-12-18 08:37:54 (GMT) |
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committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2012-12-18 20:32:56 (GMT) |
commit | b0a2658acb5bf9ca86b4aab011b7106de3af0add (patch) | |
tree | a38f27be2ee14c2114683694b0c36a8fc5c34268 /drivers/gpu | |
parent | b45305fce5bb1abec263fcff9d81ebecd6306ede (diff) | |
download | linux-b0a2658acb5bf9ca86b4aab011b7106de3af0add.tar.xz |
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>
Diffstat (limited to 'drivers/gpu')
-rw-r--r-- | drivers/gpu/drm/i915/intel_display.c | 4 |
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 82267b2..bc0b7aa 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. */ |