[PATCH 2/3] drm/xe: Add xe_ttm_access_memory

[Matthew Brost]

Non-contiguous VRAM cannot easily be mapped in TTM nor can non-visible
VRAM easily be accessed. Add xe_ttm_access_memory which hooks into
ttm_bo_access to access such memory.

Reported-by: Christoph Manszewski <christoph.manszewski at intel.com>
Suggested-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Signed-off-by: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/xe/xe_bo.c | 57 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 5b232f2951b1..9a5c1ed7ae97 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -442,6 +442,14 @@ static void xe_ttm_tt_destroy(struct ttm_device *ttm_dev, struct ttm_tt *tt)
 	kfree(tt);
 }
 
+static bool xe_ttm_resource_visible(struct ttm_resource *mem)
+{
+	struct xe_ttm_vram_mgr_resource *vres =
+		to_xe_ttm_vram_mgr_resource(mem);
+
+	return vres->used_visible_size == mem->size;
+}
+
 static int xe_ttm_io_mem_reserve(struct ttm_device *bdev,
 				 struct ttm_resource *mem)
 {
@@ -453,11 +461,9 @@ static int xe_ttm_io_mem_reserve(struct ttm_device *bdev,
 		return 0;
 	case XE_PL_VRAM0:
 	case XE_PL_VRAM1: {
-		struct xe_ttm_vram_mgr_resource *vres =
-			to_xe_ttm_vram_mgr_resource(mem);
 		struct xe_mem_region *vram = res_to_mem_region(mem);
 
-		if (vres->used_visible_size < mem->size)
+		if (!xe_ttm_resource_visible(mem))
 			return -EINVAL;
 
 		mem->bus.offset = mem->start << PAGE_SHIFT;
@@ -1111,6 +1117,50 @@ static void xe_ttm_bo_swap_notify(struct ttm_buffer_object *ttm_bo)
 	}
 }
 
+static int xe_ttm_access_memory(struct ttm_buffer_object *ttm_bo,
+				unsigned long offset, void *buf, int len,
+				int write)
+{
+	struct xe_bo *bo = ttm_to_xe_bo(ttm_bo);
+	struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
+	struct iosys_map vmap;
+	struct xe_res_cursor cursor;
+	struct xe_mem_region *vram;
+	int bytes_left = len;
+
+	xe_bo_assert_held(bo);
+
+	if (!mem_type_is_vram(ttm_bo->resource->mem_type))
+		return -EIO;
+
+	/* FIXME: Use GPU for non-visible VRAM */
+	if (!xe_ttm_resource_visible(ttm_bo->resource))
+		return -EIO;
+
+	vram = res_to_mem_region(ttm_bo->resource);
+	xe_res_first(ttm_bo->resource, offset & PAGE_MASK, bo->size, &cursor);
+
+	do {
+		unsigned long page_offset = (offset & ~PAGE_MASK);
+		int byte_count = min((int)(PAGE_SIZE - page_offset), bytes_left);
+
+		iosys_map_set_vaddr_iomem(&vmap, (u8 __iomem *)vram->mapping +
+					  cursor.start);
+		if (write)
+			xe_map_memcpy_to(xe, &vmap, page_offset, buf, byte_count);
+		else
+			xe_map_memcpy_from(xe, buf, &vmap, page_offset, byte_count);
+
+		offset += byte_count;
+		buf += byte_count;
+		bytes_left -= byte_count;
+		if (bytes_left)
+			xe_res_next(&cursor, PAGE_SIZE);
+	} while (bytes_left);
+
+	return len;
+}
+
 const struct ttm_device_funcs xe_ttm_funcs = {
 	.ttm_tt_create = xe_ttm_tt_create,
 	.ttm_tt_populate = xe_ttm_tt_populate,
@@ -1120,6 +1170,7 @@ const struct ttm_device_funcs xe_ttm_funcs = {
 	.move = xe_bo_move,
 	.io_mem_reserve = xe_ttm_io_mem_reserve,
 	.io_mem_pfn = xe_ttm_io_mem_pfn,
+	.access_memory = xe_ttm_access_memory,
 	.release_notify = xe_ttm_bo_release_notify,
 	.eviction_valuable = ttm_bo_eviction_valuable,
 	.delete_mem_notify = xe_ttm_bo_delete_mem_notify,
-- 
2.34.1