[PATCH v2] drm/i915: intel_hpd_init(): Fix suspend/resume reprobing

Lyude
2016-01-05T21:15:30Z

This fixes reprobing of display connectors on resume. After some talking
with danvet on IRC, I learned that calling drm_helper_hpd_irq_event() does
actually trigger a full reprobe of each connector's status. It turns out
this is the actual reason reprobing on resume hasn't been working (this was
observed on a T440s):

- We call hpd_init()
- We check each connector for a couple of things before marking
connector->polled with DRM_CONNECTOR_POLL_HPD, one of which is an
active encoder. Of course, a disconnected port won't have an
active encoder, so we don't add the flag to any of the
connectors.
- We call drm_helper_hpd_irq_event()
- drm_helper_irq_event() checks each connector for the
DRM_CONNECTOR_POLL_HPD flag. The only one that has it is eDP-1,
so we skip reprobing each connector except for that one.

In addition, we now avoid setting connector->polled to
DRM_CONNECTOR_POLL_HPD for MST connectors, since their reprobing is handled
by the mst helpers. This is probably what was originally intended to happen
here anyway.

Fixes: 0e32b39ceed6 ("drm/i915: add DP 1.2 MST support (v0.7)")
Cc: stable@vger.kernel.org
Signed-off-by: Lyude <cpaul@redhat.com>
---
Changes
* Use the explanation of the issue as the commit message instead
* Change the title of the commit, since this does more then just stop a check
for an encoder now
* Add "Fixes" line for the patch that introduced this regression
* Don't enable DRM_CONNECTOR_POLL_HPD for mst connectors

drivers/gpu/drm/i915/intel_hotplug.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index b177857..51ecf0b4 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -468,9 +468,9 @@ void intel_hpd_init(struct drm_i915_private *dev_priv)
list_for_each_entry(connector, &mode_config->connector_list, head) {
struct intel_connector *intel_connector = to_intel_connector(connector);
connector->polled = intel_connector->polled;
- if (connector->encoder && !connector->polled && I915_HAS_HOTPLUG(dev) && intel_connector->encoder->hpd_pin > HPD_NONE)
- connector->polled = DRM_CONNECTOR_POLL_HPD;
- if (intel_connector->mst_port)
+ if (!connector->polled && !intel_connector->mst_port &&
+ I915_HAS_HOTPLUG(dev) &&
+ intel_connector->encoder->hpd_pin > HPD_NONE)
connector->polled = DRM_CONNECTOR_POLL_HPD;
}

--
2.5.0