[PATCH 4/4] drm/i915: don't rewrite the GTT on resume v4

[jbarnes at virtuousgeek.org (Jesse Barnes)]

The BIOS shouldn't be touching this memory across suspend/resume, so
just leave it alone.  This saves us ~6ms on resume on my T420 (retested
with write combined PTEs).

v2: change gtt restore default on pre-gen4 (Chris)
    move needs_gtt_restore flag into dev_priv
v3: make sure we restore GTT on resume from hibernate (Daniel)
    use opregion support as the cutoff for restore from resume (Chris)
v4: use a better check for opregion (Chris)

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
---
 drivers/gpu/drm/i915/i915_dma.c |    4 ++++
 drivers/gpu/drm/i915/i915_drv.c |   39 +++++++++++++++++++++++++++++----------
 drivers/gpu/drm/i915/i915_drv.h |    2 ++
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 1ce7e49..622f910 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1594,6 +1594,10 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	intel_setup_gmbus(dev);
 	intel_opregion_setup(dev);
 
+	/* Gen3+ should have saner BIOSes (we hope) */
+	if (!dev_priv->opregion.header)
+		dev_priv->needs_gtt_restore = true;
+
 	/* Make sure the bios did its job and set up vital registers */
 	intel_setup_bios(dev);
 
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index dd4e43f..26a0165 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -533,19 +533,11 @@ void intel_console_resume(struct work_struct *work)
 	console_unlock();
 }
 
-static int i915_drm_thaw(struct drm_device *dev)
+static int __i915_drm_thaw(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int error = 0;
 
-	intel_gt_reset(dev);
-
-	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
-		mutex_lock(&dev->struct_mutex);
-		i915_gem_restore_gtt_mappings(dev);
-		mutex_unlock(&dev->struct_mutex);
-	}
-
 	i915_restore_state(dev);
 	intel_opregion_setup(dev);
 
@@ -584,8 +576,26 @@ static int i915_drm_thaw(struct drm_device *dev)
 	return error;
 }
 
+static int i915_drm_thaw(struct drm_device *dev)
+{
+	int error = 0;
+
+	intel_gt_reset(dev);
+
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		mutex_lock(&dev->struct_mutex);
+		i915_gem_restore_gtt_mappings(dev);
+		mutex_unlock(&dev->struct_mutex);
+	}
+
+	__i915_drm_thaw(dev);
+
+	return error;
+}
+
 int i915_resume(struct drm_device *dev)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
 	if (dev->switch_power_state == DRM_SWITCH_POWER_OFF)
@@ -596,7 +606,16 @@ int i915_resume(struct drm_device *dev)
 
 	pci_set_master(dev->pdev);
 
-	ret = i915_drm_thaw(dev);
+	intel_gt_reset(dev);
+
+	if (drm_core_check_feature(dev, DRIVER_MODESET) &&
+	    dev_priv->needs_gtt_restore) {
+		mutex_lock(&dev->struct_mutex);
+		i915_gem_restore_gtt_mappings(dev);
+		mutex_unlock(&dev->struct_mutex);
+	}
+
+	ret = __i915_drm_thaw(dev);
 	if (ret)
 		return ret;
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b41a90b..df65e48 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -881,6 +881,8 @@ typedef struct drm_i915_private {
 
 	struct delayed_work gen6_power_work;
 
+	bool needs_gtt_restore;
+
 	enum no_fbc_reason no_fbc_reason;
 
 	struct drm_mm_node *compressed_fb;
-- 
1.7.9.5