[PATCH] drm/i915: use delayed work for resume hotplug v4

[Jesse Barnes <jbarnes@virtuousgeek.org>]

Gets the detect code (which may take awhile) out of the resume path,
speeding things up a bit.

v2: use a delayed work queue instead (Daniel)
v3: cancel delayed work at unload and suspend time (Jesse)
v4: make delayed work comment less scary (Chris)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
---
 drivers/gpu/drm/i915/i915_dma.c | 12 ++++++++++++
 drivers/gpu/drm/i915/i915_drv.c | 19 +++++++++++++++++--
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 85d14e1..65001de 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1303,6 +1303,15 @@ static const struct vga_switcheroo_client_ops i915_switcheroo_ops = {
 	.can_switch = i915_switcheroo_can_switch,
 };
 
+static void intel_resume_hotplug(struct work_struct *work)
+{
+	struct drm_i915_private *dev_priv =
+		container_of(work, struct drm_i915_private,
+			     hotplug_resume_work.work);
+
+	drm_helper_hpd_irq_event(dev_priv->dev);
+}
+
 static int i915_load_modeset_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -1364,6 +1373,7 @@ static int i915_load_modeset_init(struct drm_device *dev)
 
 	/* Only enable hotplug handling once the fbdev is fully set up. */
 	intel_hpd_init(dev_priv);
+	INIT_DELAYED_WORK(&dev_priv->hotplug_resume_work, intel_resume_hotplug);
 
 	/*
 	 * Some ports require correctly set-up hpd registers for detection to
@@ -1854,6 +1864,8 @@ int i915_driver_unload(struct drm_device *dev)
 	acpi_video_unregister();
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		cancel_delayed_work(&dev_priv->hotplug_resume_work);
+
 		intel_fbdev_fini(dev);
 		intel_modeset_cleanup(dev);
 
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index a05a1d0..74fc289 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -585,6 +585,12 @@ static int i915_drm_freeze(struct drm_device *dev)
 		}
 
 		/*
+		 * In case we haven't run this by the time we resume, we may
+		 * as well cancel until we resume again.
+		 */
+		cancel_delayed_work(&dev_priv->hotplug_resume_work);
+
+		/*
 		 * Disable CRTCs directly since we want to preserve sw state
 		 * for _thaw. Also, power gate the CRTC power wells.
 		 */
@@ -726,8 +732,17 @@ static int __i915_drm_thaw(struct drm_device *dev, bool restore_gtt_mappings)
 		 * notifications.
 		 * */
 		intel_hpd_init(dev_priv);
-		/* Config may have changed between suspend and resume */
-		drm_helper_hpd_irq_event(dev);
+
+		/*
+		 * Config may have changed between suspend and resume, queue
+		 * a hotplug notification for userspace to check when it wakes
+		 * up. Delay the work slightly so that the resume has time to
+		 * finish, before userspace starts pounding at the gates
+		 * checking for changes. This speeds up the resume process by
+		 * reducing contention for resources.
+		 */
+		schedule_delayed_work(&dev_priv->hotplug_resume_work,
+				      msecs_to_jiffies(50));
 	}
 
 	intel_opregion_init(dev);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 1e476b5..6273ad6 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1521,6 +1521,7 @@ struct drm_i915_private {
 	} hpd_stats[HPD_NUM_PINS];
 	u32 hpd_event_bits;
 	struct delayed_work hotplug_reenable_work;
+	struct delayed_work hotplug_resume_work;
 
 	struct i915_fbc fbc;
 	struct i915_drrs drrs;
-- 
1.9.1