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

[Michel Dänzer]

On 08/11/16 06:23 PM, Christian König wrote:
> 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).

Do you mean GPU access to GTT? If so, not sure why it would be writes only?


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