[Intel-gfx] [PATCH 07/18] drm/i915: Defer allocation of stolen memory for FBC until actual first use

[Chris Wilson]

As FBC is commonly disabled due to limitations of the chipset upon
output configurations, on many systems FBC is never enabled. For those
systems, it is advantageous to make use of the stolen memory for other
objects and so we defer allocation of the FBC chunk until we actually
require it. This increases the likelihood of that allocation failing,
which in turns means that we are already taking advantage of the stolen
memory!

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_pm.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 9ee53cb..cbf3f38 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -440,12 +440,6 @@ void intel_update_fbc(struct drm_device *dev)
 		dev_priv->no_fbc_reason = FBC_MODULE_PARAM;
 		goto out_disable;
 	}
-	if (intel_fb->obj->base.size > i915_gem_stolen_setup_compression(dev)) {
-		DRM_DEBUG_KMS("framebuffer too large, disabling "
-			      "compression\n");
-		dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
-		goto out_disable;
-	}
 	if ((crtc->mode.flags & DRM_MODE_FLAG_INTERLACE) ||
 	    (crtc->mode.flags & DRM_MODE_FLAG_DBLSCAN)) {
 		DRM_DEBUG_KMS("mode incompatible with compression, "
@@ -479,6 +473,13 @@ void intel_update_fbc(struct drm_device *dev)
 	if (in_dbg_master())
 		goto out_disable;
 
+	if (intel_fb->obj->base.size > i915_gem_stolen_setup_compression(dev)) {
+		DRM_DEBUG_KMS("framebuffer too large, disabling "
+			      "compression\n");
+		dev_priv->no_fbc_reason = FBC_STOLEN_TOO_SMALL;
+		goto out_disable;
+	}
+
 	/* If the scanout has not changed, don't modify the FBC settings.
 	 * Note that we make the fundamental assumption that the fb->obj
 	 * cannot be unpinned (and have its GTT offset and fence revoked)
-- 
1.7.10.4