gma500: gtt based hardware scrolling console

Add support for GTT based scrolling. Instead of pushing bits around we simply
use the GTT to change the mappings. This provides us with a very fast way to
scroll the display providing we have enough memory to allocate on 4K line
boundaries. In practice this seems to be the case except for very big displays
such as HDMI, and the usual configurations are netbooks/tablets.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 48 insertions, 3 deletions

diff --git a/drivers/gpu/drm/gma500/gtt.c b/drivers/gpu/drm/gma500/gtt.c
index a24623997e50..e770bd190a5c 100644
--- a/drivers/gpu/drm/gma500/gtt.c
+++ b/drivers/gpu/drm/gma500/gtt.c
@@ -95,12 +95,17 @@ static int psb_gtt_insert(struct drm_device *dev, struct gtt_range *r)
 	set_pages_array_uc(pages, r->npage);
 
 	/* Write our page entries into the GTT itself */
-	for (i = 0; i < r->npage; i++) {
-		pte = psb_gtt_mask_pte(page_to_pfn(*pages++), 0/*type*/);
+	for (i = r->roll; i < r->npage; i++) {
+		pte = psb_gtt_mask_pte(page_to_pfn(r->pages[i]), 0);
+		iowrite32(pte, gtt_slot++);
+	}
+	for (i = 0; i < r->roll; i++) {
+		pte = psb_gtt_mask_pte(page_to_pfn(r->pages[i]), 0);
 		iowrite32(pte, gtt_slot++);
 	}
 	/* Make sure all the entries are set before we return */
 	ioread32(gtt_slot - 1);
+
 	return 0;
 }
 
@@ -113,7 +118,6 @@ static int psb_gtt_insert(struct drm_device *dev, struct gtt_range *r)
  *	page table entries with the dummy page. This is protected via the gtt
  *	mutex which the caller must hold.
  */
-
 static void psb_gtt_remove(struct drm_device *dev, struct gtt_range *r)
 {
 	struct drm_psb_private *dev_priv = dev->dev_private;
@@ -132,6 +136,46 @@ static void psb_gtt_remove(struct drm_device *dev, struct gtt_range *r)
 }
 
 /**
+ *	psb_gtt_roll	-	set scrolling position
+ *	@dev: our DRM device
+ *	@r: the gtt mapping we are using
+ *	@roll: roll offset
+ *
+ *	Roll an existing pinned mapping by moving the pages through the GTT.
+ *	This allows us to implement hardware scrolling on the consoles without
+ *	a 2D engine
+ */
+void psb_gtt_roll(struct drm_device *dev, struct gtt_range *r, int roll)
+{
+	u32 *gtt_slot, pte;
+	int i;
+
+	if (roll >= r->npage) {
+		WARN_ON(1);
+		return;
+	}
+
+	r->roll = roll;
+
+	/* Not currently in the GTT - no worry we will write the mapping at
+	   the right position when it gets pinned */
+	if (!r->stolen && !r->in_gart)
+		return;
+
+	gtt_slot = psb_gtt_entry(dev, r);
+
+	for (i = r->roll; i < r->npage; i++) {
+		pte = psb_gtt_mask_pte(page_to_pfn(r->pages[i]), 0);
+		iowrite32(pte, gtt_slot++);
+	}
+	for (i = 0; i < r->roll; i++) {
+		pte = psb_gtt_mask_pte(page_to_pfn(r->pages[i]), 0);
+		iowrite32(pte, gtt_slot++);
+	}
+	ioread32(gtt_slot - 1);
+}
+
+/**
  *	psb_gtt_attach_pages	-	attach and pin GEM pages
  *	@gt: the gtt range
  *
@@ -302,6 +346,7 @@ struct gtt_range *psb_gtt_alloc_range(struct drm_device *dev, int len,
 	gt->resource.name = name;
 	gt->stolen = backed;
 	gt->in_gart = backed;
+	gt->roll = 0;
 	/* Ensure this is set for non GEM objects */
 	gt->gem.dev = dev;
 	ret = allocate_resource(dev_priv->gtt_mem, &gt->resource,