From: Chris Wilson <[email protected]> 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 value 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 <[email protected]> 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 <[email protected]> Date: Fri Jun 8 14:53:06 2012 -0700 Revert "drm/i915/crt: Do not rely upon the HPD presence pin" Reported-and-tested-by: Matthieu LAVIE <[email protected]> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50501 Signed-off-by: Chris Wilson <[email protected]> --- drivers/gpu/drm/i915/intel_crt.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c index 75a70c4..7155181 100644 --- a/drivers/gpu/drm/i915/intel_crt.c +++ b/drivers/gpu/drm/i915/intel_crt.c @@ -453,18 +453,23 @@ 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; + if (I915_HAS_HOTPLUG(dev)) + return connector_status_disconnected; + if (!force) return connector->status; -- 1.7.10 _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
