[PATCH 1/2] drm/amdgpu: access stolen VRAM directly on KV/KB

[Christian König]

Am 08.11.2016 um 08:31 schrieb Michel Dänzer:
> On 07/11/16 06:33 PM, Christian König wrote:
>> Am 07.11.2016 um 10:29 schrieb Michel Dänzer:
>>> On 07/11/16 06:21 PM, Christian König wrote:
>>>> From: Christian König <christian.koenig at amd.com>
>>>>
>>>> We don't need to use the PCI BAR on APUs. This allows us to access
>>>> the full VRAM directly without being limited by the BAR size.
>>>>
>>>> Signed-off-by: Christian König <christian.koenig at amd.com>
>>> The series is
>>>
>>> Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>
>>>
>>>
>>> We could also drop the HDP flushes / invalidates in this case, right?
>> Could be, but I'm not 100% sure how those are actually wired up on APUs.
>>
>> Might be that they are NOPs anyway, but could be that at least the
>> flushes are still vital.
> My assumption is that since CPU access to VRAM doesn't go through the
> HDP at all with this change, HDP flushes / invalidates can't have any
> useful effect.

Well writes to GTT still use the HDP if I understand it correctly.

So we still need to handle either flushes or invalidations (I doesn't of 
hand remember which was that).

Regards,
Christian.