drm/nvc0/fb: allocate page for some unknown PFFB object

Fixes DMAR faults during accel, more than likely a similar problem to what
was solved on nv50 previously.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvc0_fb.c

 /*
- * Copyright 2010 Red Hat Inc.
+ * Copyright 2011 Red Hat Inc.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -23,16 +23,80 @@
  */
 
 #include "drmP.h"
-
+#include "drm.h"
 #include "nouveau_drv.h"
+#include "nouveau_drm.h"
+
+struct nvc0_fb_priv {
+	struct page *r100c10_page;
+	dma_addr_t r100c10;
+};
+
+static void
+nvc0_fb_destroy(struct drm_device *dev)
+{
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+	struct nouveau_fb_engine *pfb = &dev_priv->engine.fb;
+	struct nvc0_fb_priv *priv = pfb->priv;
+
+	if (priv->r100c10_page) {
+		pci_unmap_page(dev->pdev, priv->r100c10, PAGE_SIZE,
+			       PCI_DMA_BIDIRECTIONAL);
+		__free_page(priv->r100c10_page);
+	}
+
+	kfree(priv);
+	pfb->priv = NULL;
+}
+
+static int
+nvc0_fb_create(struct drm_device *dev)
+{
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+	struct nouveau_fb_engine *pfb = &dev_priv->engine.fb;
+	struct nvc0_fb_priv *priv;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	pfb->priv = priv;
+
+	priv->r100c10_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (!priv->r100c10_page) {
+		nvc0_fb_destroy(dev);
+		return -ENOMEM;
+	}
+
+	priv->r100c10 = pci_map_page(dev->pdev, priv->r100c10_page, 0,
+				     PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
+	if (pci_dma_mapping_error(dev->pdev, priv->r100c10)) {
+		nvc0_fb_destroy(dev);
+		return -EFAULT;
+	}
+
+	return 0;
+}
 
 int
 nvc0_fb_init(struct drm_device *dev)
 {
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+	struct nvc0_fb_priv *priv;
+	int ret;
+
+	if (!dev_priv->engine.fb.priv) {
+		ret = nvc0_fb_create(dev);
+		if (ret)
+			return ret;
+	}
+	priv = dev_priv->engine.fb.priv;
+
+	nv_wr32(dev, 0x100c10, priv->r100c10 >> 8);
 	return 0;
 }
 
 void
 nvc0_fb_takedown(struct drm_device *dev)
 {
+	nvc0_fb_destroy(dev);
 }