[PATCH] drm/amdgpu: use ttm pool first

[Christian König]

Am 24.01.2018 um 10:49 schrieb 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

Oh! Good point, didn't noticed that bug before. But yes the rational 
makes perfect sense.

Regards,
Christian.