drm/i915: Use the agp_size determined from the GTT

This is the same value as before, but it just makes the code slightly
more readable to use the local variable than converting the aperture
size into bytes every time.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 1bd37e3..d8def48 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1920,6 +1920,16 @@
 	if (IS_GEN2(dev))
 		dma_set_coherent_mask(&dev->pdev->dev, DMA_BIT_MASK(30));
 
+	dev_priv->mm.gtt = intel_gtt_get();
+	if (!dev_priv->mm.gtt) {
+		DRM_ERROR("Failed to initialize GTT\n");
+		ret = -ENODEV;
+		goto out_iomapfree;
+	}
+
+	prealloc_size = dev_priv->mm.gtt->gtt_stolen_entries << PAGE_SHIFT;
+	agp_size = dev_priv->mm.gtt->gtt_mappable_entries << PAGE_SHIFT;
+
 	dev_priv->regs = ioremap(base, size);
 	if (!dev_priv->regs) {
 		DRM_ERROR("failed to map registers\n");
@@ -1928,8 +1938,7 @@
 	}
 
         dev_priv->mm.gtt_mapping =
-		io_mapping_create_wc(dev->agp->base,
-				     dev->agp->agp_info.aper_size * 1024*1024);
+		io_mapping_create_wc(dev->agp->base, agp_size);
 	if (dev_priv->mm.gtt_mapping == NULL) {
 		ret = -EIO;
 		goto out_rmmap;
@@ -1941,24 +1950,13 @@
 	 * MTRR if present.  Even if a UC MTRR isn't present.
 	 */
 	dev_priv->mm.gtt_mtrr = mtrr_add(dev->agp->base,
-					 dev->agp->agp_info.aper_size *
-					 1024 * 1024,
+					 agp_size,
 					 MTRR_TYPE_WRCOMB, 1);
 	if (dev_priv->mm.gtt_mtrr < 0) {
 		DRM_INFO("MTRR allocation failed.  Graphics "
 			 "performance may suffer.\n");
 	}
 
-	dev_priv->mm.gtt = intel_gtt_get();
-	if (!dev_priv->mm.gtt) {
-		DRM_ERROR("Failed to initialize GTT\n");
-		ret = -ENODEV;
-		goto out_iomapfree;
-	}
-
-	prealloc_size = dev_priv->mm.gtt->gtt_stolen_entries << PAGE_SHIFT;
-	agp_size = dev_priv->mm.gtt->gtt_mappable_entries << PAGE_SHIFT;
-
 	/* The i915 workqueue is primarily used for batched retirement of
 	 * requests (and thus managing bo) once the task has been completed
 	 * by the GPU. i915_gem_retire_requests() is called directly when we