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

    drm/i915: Avoid GPU hang when coming out of s3 or s4

to the 4.0-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-avoid-gpu-hang-when-coming-out-of-s3-or-s4.patch
and it can be found in the queue-4.0 subdirectory.

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


>From 364aece01a2dd748fc36a1e8bf52ef639b0857bd Mon Sep 17 00:00:00 2001
From: Peter Antoine <[email protected]>
Date: Mon, 11 May 2015 08:50:45 +0100
Subject: drm/i915: Avoid GPU hang when coming out of s3 or s4

From: Peter Antoine <[email protected]>

commit 364aece01a2dd748fc36a1e8bf52ef639b0857bd upstream.

This patch fixes a timing issue that causes a GPU hang when the system
comes out of power saving.

During pm_resume, We are submitting batchbuffers before enabling
Interrupts this is causing us to miss the context switch interrupt,
and in consequence intel_execlists_handle_ctx_events is not triggered.

This patch is based on a patch from Deepak S <[email protected]>
from another platform.

The patch fixes an issue introduced by:
  commit e7778be1eab918274f79603d7c17b3ec8be77386
  drm/i915: Fix startup failure in LRC mode after recent init changes

The above patch added a call to init_context() to fix an issue introduced
by a previous patch. But, it then opened up a small timing window for the
batches being added by the init_context (basically setting up the context)
to complete before the interrupts have been turned on, thus hanging the
GPU.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89600
Cc: [email protected] # 4.0+
Signed-off-by: Peter Antoine <[email protected]>
Reviewed-by: Daniel Vetter <[email protected]>
[Jani: fixed typo in subject, massaged the comments a bit]
Signed-off-by: Jani Nikula <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/gpu/drm/i915/i915_drv.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -693,6 +693,16 @@ static int i915_drm_resume(struct drm_de
                intel_init_pch_refclk(dev);
                drm_mode_config_reset(dev);
 
+               /*
+                * Interrupts have to be enabled before any batches are run.
+                * If not the GPU will hang. i915_gem_init_hw() will initiate
+                * batches to update/restore the context.
+                *
+                * Modeset enabling in intel_modeset_init_hw() also needs
+                * working interrupts.
+                */
+               intel_runtime_pm_enable_interrupts(dev_priv);
+
                mutex_lock(&dev->struct_mutex);
                if (i915_gem_init_hw(dev)) {
                        DRM_ERROR("failed to re-initialize GPU, declaring 
wedged!\n");
@@ -700,9 +710,6 @@ static int i915_drm_resume(struct drm_de
                }
                mutex_unlock(&dev->struct_mutex);
 
-               /* We need working interrupts for modeset enabling ... */
-               intel_runtime_pm_enable_interrupts(dev_priv);
-
                intel_modeset_init_hw(dev);
 
                spin_lock_irq(&dev_priv->irq_lock);


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

queue-4.0/drm-i915-avoid-gpu-hang-when-coming-out-of-s3-or-s4.patch
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