diff options
author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2012-06-16 15:30:32 +0200 |
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committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2012-06-16 15:30:32 +0200 |
commit | aaa377302b2994fcc2c66741b47da33feb489dca (patch) | |
tree | 184ed8537cc264d64f93553569c0d03da6a94f9e | |
parent | 8e96d9c4d9843f00ebeb4a9b33596d96602ea101 (diff) |
drm/i915/crt: Do not rely upon the HPD presence pin
VGA hotplug detection "works" by measuring the resistance across
certain pins. A lot of kvm switches fumble this and wire up cheap
resistors with the wrong resistance or don't bother at all.
To accomodate these, also try to detect a connected monitor by trying
to grab the edid. Contrary to !HAS_HOTPLUG platforms we don't bother
with an actual load-detection cycle when the output is life - that
would be actual work to implement because things moved around. This is
the big difference to Chris Wilson's original approach:
commit 9e612a008fa7fe493a473454def56aa321479495
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu May 31 13:08:53 2012 +0100
drm/i915/crt: Do not rely upon the HPD presence pin
This blew up on Linus' machine because it errornously detected a vga
screen (without and edid and hence only the default modes), leading to
it's prompt removal:
commit 8f53369b753f5f4c7684c2eb0b592152abb1dd00
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri Jun 8 14:53:06 2012 -0700
Revert "drm/i915/crt: Do not rely upon the HPD presence pin"
Some digging around in Bspec shows the reason why load detect doesn't work on
newer chips - the legacy VGA load detect bit isn't wired up any longer:
Public Snb Bspec, Vol3 Part1, 1.1.1 ST00 Input Status 0, bit4:
"RGB Comparator / Sense. This bit is here for compatibility and will
always return one. Monitor detection must be done be done through the
programming of registers in the MMIO space.
0 = Below threshold
1 = Above threshold"
v2: Add a comment in the code that load detect on hotplug capable
machines is broken and pimp the commit message with a quote of Bspec
to show why.
Reported-and-tested-by: Matthieu LAVIE <boiteamadmax@hotmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50501
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
-rw-r--r-- | drivers/gpu/drm/i915/intel_crt.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c index 75a70c46ef1..5978490dac9 100644 --- a/drivers/gpu/drm/i915/intel_crt.c +++ b/drivers/gpu/drm/i915/intel_crt.c @@ -453,18 +453,27 @@ intel_crt_detect(struct drm_connector *connector, bool force) struct intel_load_detect_pipe tmp; if (I915_HAS_HOTPLUG(dev)) { + /* We can not rely on the HPD pin always being correctly wired + * up, for example many KVM do not pass it through, and so + * only trust an assertion that the monitor is connected. + */ if (intel_crt_detect_hotplug(connector)) { DRM_DEBUG_KMS("CRT detected via hotplug\n"); return connector_status_connected; - } else { + } else DRM_DEBUG_KMS("CRT not detected via hotplug\n"); - return connector_status_disconnected; - } } if (intel_crt_detect_ddc(connector)) return connector_status_connected; + /* Load detection is broken on HPD capable machines. Whoever wants a + * broken monitor (without edid) to work behind a broken kvm (that fails + * to have the right resistors for HP detection) needs to fix this up. + * For now just bail out. */ + if (I915_HAS_HOTPLUG(dev)) + return connector_status_disconnected; + if (!force) return connector->status; |