Patch "Revert "drm/radeon: call hpd_irq_event on 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

Revert "drm/radeon: call hpd_irq_event on 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:
revert-drm-radeon-call-hpd_irq_event-on-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: Linus Torvalds <[email protected]>
Date: Mon, 7 Mar 2016 13:15:09 -0800
Subject: Revert "drm/radeon: call hpd_irq_event on resume"
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From: Linus Torvalds <[email protected]>

commit 256faedcfd646161477d47a1a78c32a562d2e845 upstream.

This reverts commit dbb17a21c131eca94eb31136eee9a7fe5aff00d9.

It turns out that commit can cause problems for systems with multiple GPUs, and causes X to hang on at least a HP Pavilion dv7 with hybrid graphics.

This got noticed originally in 4.4.4, where this patch had already gotten back-ported, but 4.5-rc7 was verified to have the same problem.

Alexander Deucher says:
"It looks like you have a muxed system so I suspect what's happening is
that one of the display is being reported as connected for both the IGP and the dGPU and then the desktop environment gets confused or there some sort problem in the detect functions since the mux is not switched to the dGPU. I don't see an easy fix unless Dave has any ideas. I'd say just revert for now"

---
 drivers/gpu/drm/radeon/radeon_device.c |    1 -
 1 file changed, 1 deletion(-)

@@ -1744,7 +1744,6 @@ int radeon_resume_kms(struct drm_device
 	}
 
 	drm_kms_helper_poll_enable(dev);
-	drm_helper_hpd_irq_event(dev);
 
 	/* set the power state here in case we are a PX system or headless */
 	if ((rdev->pm.pm_method == PM_METHOD_DPM) && rdev->pm.dpm_enabled)

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

queue-4.4/revert-drm-radeon-call-hpd_irq_event-on-resume.patch