[PATCH] drm/amdgpu: Support >=4GB GTT memory mapping

[Philip Yang]

This is to work around a bug in function drm_prime_pages_to_sg if length
of nr_pages >= 4GB, by doing the same check for max_segment and then
calling sg_alloc_table_from_pages_segment directly instead.

This issue shows up on APU because VRAM is allocated as GTT memory. It
also fixes >=4GB GTT memory mapping for mGPUs with IOMMU isolation mode.

Signed-off-by: Philip Yang <Philip.Yang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 50 ++++++++++++++-------
 1 file changed, 34 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
index 055ba2ea4c12..a203633fd629 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
@@ -171,18 +171,41 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
 	}
 
 	switch (bo->tbo.resource->mem_type) {
-	case TTM_PL_TT:
-		sgt = drm_prime_pages_to_sg(obj->dev,
-					    bo->tbo.ttm->pages,
-					    bo->tbo.ttm->num_pages);
-		if (IS_ERR(sgt))
-			return sgt;
-
-		if (dma_map_sgtable(attach->dev, sgt, dir,
-				    DMA_ATTR_SKIP_CPU_SYNC))
-			goto error_free;
-		break;
+	case TTM_PL_TT: {
+		size_t max_segment = 0;
+		u64 num_pages;
+		int err;
+
+		sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
+		if (!sgt)
+			return ERR_PTR(-ENOMEM);
+
+		if (obj->dev)
+			max_segment = dma_max_mapping_size(obj->dev->dev);
+		if (max_segment == 0)
+			max_segment = UINT_MAX;
+
+		/*
+		 * Use u64, otherwise if length of num_pages >= 4GB then size
+		 * (num_pages << PAGE_SHIFT) becomes 0
+		 */
+		num_pages = bo->tbo.ttm->num_pages;
+		err = sg_alloc_table_from_pages_segment(sgt, bo->tbo.ttm->pages,
+							num_pages, 0,
+							num_pages << PAGE_SHIFT,
+							max_segment, GFP_KERNEL);
+		if (err) {
+			kfree(sgt);
+			return ERR_PTR(err);
+		}
 
+		if (dma_map_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC)) {
+			sg_free_table(sgt);
+			kfree(sgt);
+			return ERR_PTR(-EBUSY);
+		}
+		break;
+	}
 	case TTM_PL_VRAM:
 		r = amdgpu_vram_mgr_alloc_sgt(adev, bo->tbo.resource, 0,
 					      bo->tbo.base.size, attach->dev,
@@ -195,11 +218,6 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
 	}
 
 	return sgt;
-
-error_free:
-	sg_free_table(sgt);
-	kfree(sgt);
-	return ERR_PTR(-EBUSY);
 }
 
 /**
-- 
2.35.1