[Intel-gfx] [PATCH 3/3] drm/i915: don't rewrite the GTT on resume

[Jesse Barnes]

The BIOS shouldn't be touching this memory across suspend/resume, so
just leave it alone.  This saves us ~50ms on resume on my T420.

Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
---
 drivers/gpu/drm/i915/i915_drv.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 824e3c8..95e2b8b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -119,6 +119,10 @@ module_param_named(i915_enable_ppgtt, i915_enable_ppgtt, int, 0600);
 MODULE_PARM_DESC(i915_enable_ppgtt,
 		"Enable PPGTT (default: true)");
 
+int i915_needs_gtt_restore __read_mostly = 0;
+module_param_named(gtt_restore, i915_needs_gtt_restore, int, 0600);
+MODULE_PARM_DESC(gtt_restore, "Rewrite GTT on resume (default: false)");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
@@ -537,7 +541,8 @@ static int i915_drm_thaw(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int error = 0;
 
-	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+	if (drm_core_check_feature(dev, DRIVER_MODESET) &&
+	    i915_needs_gtt_restore) {
 		mutex_lock(&dev->struct_mutex);
 		i915_gem_restore_gtt_mappings(dev);
 		mutex_unlock(&dev->struct_mutex);
-- 
1.7.9.5