[PATCH] drm/i915: Suppress hotplug work during PM suspend/resume

[Takashi Iwai <tiwai@suse.de>]

The hotplug work can be still kicked off via irq during PM, and this
may conflict with the resume procedure.  For example, eDP on SNB
machine shows WARNING like below during the resume:

  WARNING: at /usr/src/packages/BUILD/kernel-default-3.0.13/linux-3.0/drivers/gpu/drm/i915/intel_dp.c:332 intel_dp_check_edp+0x73/0xd0 [i915]()
  Hardware name: HP Z1 Workstation
  eDP powered off while attempting aux channel communication.
  Supported: Yes
  Pid: 3210, comm: kworker/u:49 Tainted: G         C N  3.0.13-0.27-default #1
  Call Trace:
   [<ffffffff810048b5>] dump_trace+0x75/0x300
   [<ffffffff8143ea0f>] dump_stack+0x69/0x6f
   [<ffffffff81059e2b>] warn_slowpath_common+0x7b/0xc0
   [<ffffffff81059f25>] warn_slowpath_fmt+0x45/0x50
   [<ffffffffa01fa9f3>] intel_dp_check_edp+0x73/0xd0 [i915]
   [<ffffffffa01fae4b>] intel_dp_aux_native_write+0x1b/0xe0 [i915]
   [<ffffffffa01fb033>] intel_dp_set_link_train+0x73/0xa0 [i915]
   [<ffffffffa01fb58e>] intel_dp_start_link_train+0x16e/0x400 [i915]
   [<ffffffffa01fbc6c>] intel_dp_complete_link_train+0x1fc/0x3d0 [i915]
   [<ffffffffa01fcf4c>] intel_dp_check_link_status+0x12c/0x1d0 [i915]
   [<ffffffffa01cf22e>] i915_hotplug_work_func+0x6e/0xa0 [i915]
   [<ffffffff810747bc>] process_one_work+0x16c/0x350
   [<ffffffff8107734a>] worker_thread+0x17a/0x410
   [<ffffffff8107b676>] kthread+0x96/0xa0
   [<ffffffff8144a7c4>] kernel_thread_helper+0x4/0x10
  DWARF2 unwinder stuck at kernel_thread_helper+0x4/0x10

This patch adds a flag to disable the hotplug during PM operation for
avoiding such a race.

Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---

It's a pretty simplistic solution that just ignores the hotplug work.
We may keep some pending flag and process it later, if ignoring the
event matters...

 drivers/gpu/drm/i915/i915_drv.c |    2 ++
 drivers/gpu/drm/i915/i915_drv.h |    1 +
 drivers/gpu/drm/i915/i915_irq.c |    9 ++++++---
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index ae8a64f..dcbc8be 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -471,6 +471,7 @@ static int i915_drm_freeze(struct drm_device *dev)
 
 	/* Modeset on resume, not lid events */
 	dev_priv->modeset_on_lid = 0;
+	dev_priv->disable_hotplug_in_pm = true;
 
 	console_lock();
 	intel_fbdev_set_suspend(dev, 1);
@@ -548,6 +549,7 @@ static int i915_drm_thaw(struct drm_device *dev)
 
 	intel_opregion_init(dev);
 
+	dev_priv->disable_hotplug_in_pm = false;
 	dev_priv->modeset_on_lid = 0;
 
 	console_lock();
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5fabc6c..80d38ce 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -360,6 +360,7 @@ typedef struct drm_i915_private {
 	u32 gt_irq_mask;
 	u32 pch_irq_mask;
 
+	bool disable_hotplug_in_pm;
 	u32 hotplug_supported_mask;
 	struct work_struct hotplug_work;
 
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index afd4e03..f56f4bc 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -527,7 +527,8 @@ static irqreturn_t ivybridge_irq_handler(DRM_IRQ_ARGS)
 
 	/* check event from PCH */
 	if (de_iir & DE_PCH_EVENT_IVB) {
-		if (pch_iir & SDE_HOTPLUG_MASK_CPT)
+		if (!dev_priv->disable_hotplug_in_pm &&
+		    (pch_iir & SDE_HOTPLUG_MASK_CPT))
 			queue_work(dev_priv->wq, &dev_priv->hotplug_work);
 		pch_irq_handler(dev);
 	}
@@ -627,7 +628,8 @@ static irqreturn_t ironlake_irq_handler(DRM_IRQ_ARGS)
 
 	/* check event from PCH */
 	if (de_iir & DE_PCH_EVENT) {
-		if (pch_iir & hotplug_mask)
+		if (!dev_priv->disable_hotplug_in_pm &&
+		    (pch_iir & hotplug_mask))
 			queue_work(dev_priv->wq, &dev_priv->hotplug_work);
 		pch_irq_handler(dev);
 	}
@@ -1345,7 +1347,8 @@ static irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 
 			DRM_DEBUG_DRIVER("hotplug event received, stat 0x%08x\n",
 				  hotplug_status);
-			if (hotplug_status & dev_priv->hotplug_supported_mask)
+			if (!dev_priv->disable_hotplug_in_pm &&
+			    (hotplug_status & dev_priv->hotplug_supported_mask))
 				queue_work(dev_priv->wq,
 					   &dev_priv->hotplug_work);
 
-- 
1.7.9.2