[PATCH] drm/amdgpu: use ttm pool first

[Michel Dänzer]

On 2018-01-24 10:43 AM, Christian König wrote:
> Am 24.01.2018 um 10:17 schrieb Chunming Zhou:
>> dma path is low than ttm pool.
> 
> That won't work correctly in some cases.
> 
>> Question:
>> But why need two path? What spicific problem can be solved by dma path?
> 
> That is mostly for ARM and some (rare) x86 platforms without IOMMU where
> some memory is above the 40bit limit in the PCIe address space.
> 
> Our GPUs can unfortunately only deal with 40bits of address space, so on
> those systems we need to go the slow path and make sure that we don't
> try to touch that high memory.
> 
> What we could really improve is the detection using swiotlb_nr_tbl(),
> cause that is actually completely wrong.

FWIW, there are other cases where SWIOTLB is needed, e.g. Secure Memory
Encryption: https://bugs.freedesktop.org/show_bug.cgi?id=104437


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer