[PATCH 3/5] drm/i915/dmabuf: Add LMEM knowledge to dmabuf map handler

[Michael J. Ruhl]

LMEM backed buffer objects do not have struct page information.
Instead the dma_address of the struct sg is used to store the
LMEM address information (relative to the device, this is not
the CPU physical address).

The dmabuf map handler requires pages to do a dma_map_xx.

Add new mapping/unmapping functions, based on the LMEM usage
of the dma_address to allow LMEM backed buffer objects to be
mapped.

Before mapping check the peer2peer distance to verify that P2P
dma can occur.

Signed-off-by: Michael J. Ruhl <michael.j.ruhl at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 82 ++++++++++++++++++++--
 1 file changed, 76 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index 7ea4abb6a896..402c989cc23d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -7,6 +7,7 @@
 #include <linux/dma-buf.h>
 #include <linux/highmem.h>
 #include <linux/dma-resv.h>
+#include <linux/pci-p2pdma.h>
 #include <linux/scatterlist.h>
 
 #include "i915_drv.h"
@@ -18,6 +19,67 @@ static struct drm_i915_gem_object *dma_buf_to_obj(struct dma_buf *buf)
 	return to_intel_bo(buf->priv);
 }
 
+static void dmabuf_unmap_addr(struct device *dev, struct scatterlist *sgl,
+			      int nents, enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nents, i)
+		dma_unmap_resource(dev, sg_dma_address(sg), sg_dma_len(sg),
+				   dir, 0);
+}
+
+/**
+ * dmabuf_map_addr - Update LMEM address to a physical address and map the
+ * resource.
+ * @dev: valid device
+ * @obj: valid i915 GEM object
+ * @sg: scatter list to appy mapping to
+ * @nents: number of entries in the scatter list
+ * @dir: DMA direction
+ *
+ * The dma_address of the scatter list is the LMEM "address".  From this the
+ * actual physical address can be determined.
+ *
+ * Return of 0 means error.
+ *
+ */
+static int dmabuf_map_addr(struct device *dev, struct drm_i915_gem_object *obj,
+			   struct scatterlist *sgl, int nents,
+			   enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	phys_addr_t addr;
+	int distance;
+	int i;
+
+	distance = pci_p2pdma_distance_many(obj->base.dev->pdev, &dev, 1,
+					    true);
+	if (distance < 0) {
+		pr_info("%s: from: %s  to: %s  distance: %d\n", __func__,
+			pci_name(obj->base.dev->pdev), dev_name(dev),
+			distance);
+		return 0;
+	}
+
+	for_each_sg(sgl, sg, nents, i) {
+		addr = sg_dma_address(sg) + obj->mm.region->io_start;
+
+		sg->dma_address = dma_map_resource(dev, addr, sg->length, dir,
+						   0);
+		if (dma_mapping_error(dev, sg->dma_address))
+			goto unmap;
+		sg->dma_length = sg->length;
+	}
+
+	return nents;
+
+unmap:
+	dmabuf_unmap_addr(dev, sgl, i, dir);
+	return 0;
+}
+
 static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attach,
 					     enum dma_data_direction dir)
 {
@@ -44,12 +106,17 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attach,
 	dst = sgt->sgl;
 	for_each_sg(obj->mm.pages->sgl, src, obj->mm.pages->nents, i) {
 		sg_set_page(dst, sg_page(src), src->length, 0);
+		sg_dma_address(dst) = sg_dma_address(src);
 		dst = sg_next(dst);
 	}
 
-	if (!dma_map_sg_attrs(attach->dev,
-			      sgt->sgl, sgt->nents, dir,
-			      DMA_ATTR_SKIP_CPU_SYNC)) {
+	if (i915_gem_object_has_struct_page(obj))
+		ret = dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
+				       DMA_ATTR_SKIP_CPU_SYNC);
+	else
+		ret = dmabuf_map_addr(attach->dev, obj, sgt->sgl, sgt->nents,
+				      dir);
+	if (!ret) {
 		ret = -ENOMEM;
 		goto err_free_sg;
 	}
@@ -72,9 +139,12 @@ static void i915_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
 {
 	struct drm_i915_gem_object *obj = dma_buf_to_obj(attach->dmabuf);
 
-	dma_unmap_sg_attrs(attach->dev,
-			   sgt->sgl, sgt->nents, dir,
-			   DMA_ATTR_SKIP_CPU_SYNC);
+	if (i915_gem_object_has_struct_page(obj))
+		dma_unmap_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
+				   DMA_ATTR_SKIP_CPU_SYNC);
+	else
+		dmabuf_unmap_addr(attach->dev, sgt->sgl, sgt->nents, dir);
+
 	sg_free_table(sgt);
 	kfree(sgt);
 
-- 
2.21.0