drm/amdgpu: fix scatter-gather mapping with user pages
Shane Francis authored
Calls to dma_map_sg may return less segments / entries than requested
if they fall on page bounderies. The old implementation did not
support this use case.

Fixes: be62dbf5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api")
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=206461
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=206895
Bug: https://gitlab.freedesktop.org/drm/amd/issues/1056

Signed-off-by: default avatarShane Francis <bigbeeshane@gmail.com>
Reviewed-by: default avatarMichael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200325090741.21957-3-bigbeeshane@gmail.com
Cc: stable@vger.kernel.org
0199172f
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