agp/intel-gtt: export the scratch page dma address

To implement a PPGTT for drm/i915 that fully aliases the GTT, we also
need to properly alias the scratch page.
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/char/agp/intel-gtt.c

@@ -76,7 +76,6 @@ static struct _intel_private {
 	struct resource ifp_resource;
 	int resource_valid;
 	struct page *scratch_page;
-	dma_addr_t scratch_page_dma;
 } intel_private;
 
 #define INTEL_GTT_GEN	intel_private.driver->gen
@@ -306,9 +305,9 @@ static int intel_gtt_setup_scratch_page(void)
 		if (pci_dma_mapping_error(intel_private.pcidev, dma_addr))
 			return -EINVAL;
 
-		intel_private.scratch_page_dma = dma_addr;
+		intel_private.base.scratch_page_dma = dma_addr;
 	} else
-		intel_private.scratch_page_dma = page_to_phys(page);
+		intel_private.base.scratch_page_dma = page_to_phys(page);
 
 	intel_private.scratch_page = page;
 
@@ -631,7 +630,7 @@ static unsigned int intel_gtt_mappable_entries(void)
 static void intel_gtt_teardown_scratch_page(void)
 {
 	set_pages_wb(intel_private.scratch_page, 1);
-	pci_unmap_page(intel_private.pcidev, intel_private.scratch_page_dma,
+	pci_unmap_page(intel_private.pcidev, intel_private.base.scratch_page_dma,
 		       PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
 	put_page(intel_private.scratch_page);
 	__free_page(intel_private.scratch_page);
@@ -975,7 +974,7 @@ void intel_gtt_clear_range(unsigned int first_entry, unsigned int num_entries)
 	unsigned int i;
 
 	for (i = first_entry; i < (first_entry + num_entries); i++) {
-		intel_private.driver->write_entry(intel_private.scratch_page_dma,
+		intel_private.driver->write_entry(intel_private.base.scratch_page_dma,
 						  i, 0);
 	}
 	readl(intel_private.gtt+i-1);

include/drm/intel-gtt.h

@@ -15,6 +15,8 @@ const struct intel_gtt {
 	unsigned int needs_dmar : 1;
 	/* Whether we idle the gpu before mapping/unmapping */
 	unsigned int do_idle_maps : 1;
+	/* Share the scratch page dma with ppgtts. */
+	dma_addr_t scratch_page_dma;
 } *intel_gtt_get(void);
 
 void intel_gtt_chipset_flush(void);