This patch set is to fix a bug in amdgpu / radeon drm that results in
a crash when dma_map_sg combines elemnets within a scatterlist table. 

There are 2 shortfalls in the current kernel.

1) AMDGPU / RADEON assumes that the requested and created scatterlist
   table lengths using from dma_map_sg are equal. This may not be the
   case using the newer dma-iommu implementation

2) drm_prime does not fetch the length of the scatterlist
   via the correct dma macro, this can use the incorrect length
   being used (>0) in places where dma_map_sg has updated the table

   The sg_dma_len macro is representative of the length of the sg item
   after dma_map_sg

Example Crash :
> [drm:amdgpu_ttm_backend_bind [amdgpu]] *ERROR* failed to pin userptr

This happens in OpenCL applications, causing them to crash or hang, on
either amdgpu-pro or ROCm OpenCL implementations

I have verified this fixes the above on kernel 5.5 and 5.5rc using an
AMD Vega 64 GPU

Shane Francis (3):
  drm/prime: use dma length macro when mapping sg to arrays
  drm/amdgpu: fix scatter-gather mapping with user pages
  drm/radeon: fix scatter-gather mapping with user pages

 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +-
 drivers/gpu/drm/drm_prime.c             | 2 +-
 drivers/gpu/drm/radeon/radeon_ttm.c     | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)


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