Patch "drm/i915: intel_hpd_init(): Fix suspend/resume reprobing" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915: intel_hpd_init(): Fix suspend/resume reprobing

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-intel_hpd_init-fix-suspend-resume-reprobing.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Lyude <[email protected]>
Date: Thu, 7 Jan 2016 10:43:28 -0500
Subject: drm/i915: intel_hpd_init(): Fix suspend/resume reprobing

From: Lyude <[email protected]>

commit 2dc2f761dea65069485110d24eaa5b0d5d808b07 upstream.

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 that one.

In addition, we also 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.

Changes since V1:
* 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

Changes since V2:
* Put patch changelog above Signed-off-by
* Follow Daniel Vetter's suggestion for making the code here a bit more legible

---
 drivers/gpu/drm/i915/intel_hotplug.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

@@ -468,9 +468,14 @@ void intel_hpd_init(struct drm_i915_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;
+
+		/* MST has a dynamic intel_connector->encoder and it's reprobing
+		 * is all handled by the MST helpers. */
 		if (intel_connector->mst_port)
+			continue;
+
+		if (!connector->polled && I915_HAS_HOTPLUG(dev) &&
+		    intel_connector->encoder->hpd_pin > HPD_NONE)
 			connector->polled = DRM_CONNECTOR_POLL_HPD;
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drm-i915-skl-don-t-skip-mst-encoders-in-skl_ddi_pll_select.patch queue-4.4/drm-i915-intel_hpd_init-fix-suspend-resume-reprobing.patch