Patch "drm/nouveau: Don't enabling polling twice on runtime resume" 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/nouveau: Don't enabling polling twice on runtime resume

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-nouveau-don-t-enabling-polling-twice-on-runtime-resume.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 Paul <[email protected]>
Date: Wed, 11 Jan 2017 21:25:23 -0500
Subject: drm/nouveau: Don't enabling polling twice on runtime resume

From: Lyude Paul <[email protected]>

[ Upstream commit cae9ff036eea577856d5b12860b4c79c5e71db4a ]

As it turns out, on cards that actually have CRTCs on them we're already calling drm_kms_helper_poll_enable(drm_dev) from nouveau_display_resume() before we call it in nouveau_pmops_runtime_resume(). This leads us to accidentally trying to enable polling twice, which results in a potential deadlock between the RPM locks and drm_dev->mode_config.mutex if we end up trying to enable polling the second time while output_poll_execute is running and holding the mode_config lock. As such, make sure we only enable polling in nouveau_pmops_runtime_resume() if we need to.

This fixes hangs observed on the ThinkPad W541

---
 drivers/gpu/drm/nouveau/nouveau_display.c |    3 ++-
 drivers/gpu/drm/nouveau/nouveau_drm.c     |    5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

@@ -370,7 +370,8 @@ nouveau_display_init(struct drm_device *
 		return ret;
 
 	/* enable polling for external displays */
-	drm_kms_helper_poll_enable(dev);
+	if (!dev->mode_config.poll_enabled)
+		drm_kms_helper_poll_enable(dev);
 
 	/* enable hotplug interrupts */
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {

@@ -743,7 +743,10 @@ nouveau_pmops_runtime_resume(struct devi
 	pci_set_master(pdev);
 
 	ret = nouveau_do_resume(drm_dev, true);
-	drm_kms_helper_poll_enable(drm_dev);
+
+	if (!drm_dev->mode_config.poll_enabled)
+		drm_kms_helper_poll_enable(drm_dev);
+
 	/* do magic */
 	nvif_mask(&device->object, 0x088488, (1 << 25), (1 << 25));
 	vga_switcheroo_set_dynamic_switch(pdev, VGA_SWITCHEROO_ON);

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

queue-4.4/drm-nouveau-don-t-enabling-polling-twice-on-runtime-resume.patch