[PATCH] drm/amdgpu: fix drm leases being broken on radv

[Michel Dänzer]

On 2019-04-18 11:11 a.m., Daniel Vetter wrote:
> On Thu, Apr 18, 2019 at 10:52 AM Michel Dänzer <michel at daenzer.net> wrote:
>> On 2019-04-18 10:26 a.m., Daniel Vetter wrote:
>>>
>>> Ok correction: amd has stuck out in the past too, there was some vblank vs
>>> pageflip stuff where we needed to do some pretty clever tricks to both
>>> have the new stricter semantics for everyone, while keeping the amd ddx
>>> happy still. This aint new at all, we fixed up the regressions and moved
>>> on.
>>
>> That sounds like something I would have been involved in, but I'm not
>> sure what you mean...
>>
>> I fixed the amdgpu/radeon kernel drivers to obey the general KMS rules
>> for vblank vs page flips, and added DRM_MODE_PAGE_FLIP_TARGET to allow
>> userspace to take advantage of our hardware's capabilities to avoid
>> delaying a page flip by one refresh cycle in some cases. That's all.
> 
> That's the one I meant. At least I remember quite a pile of
> discussions around why i915 gets to define how this stuff works, and
> amdgpu/radeon having to follow.
> 
> [...]
> 
> - the vblank vs flip clarifiation that required new uapi and upgraded
> amd ddx (really not pretty if we have to somewhat break a performance
> feature for some users)

You're totally mis-representing that IMO.

The amdgpu/radeon kernel drivers were simply broken WRT established UAPI
rules, in a way which affected our DDX drivers as well. The kernel
driver fixes didn't require any corresponding userspace changes.

New UAPI was added to allow taking advantage of hardware capabilities in
some cases without breaking other cases.

It's a pretty text-book example of how to manage UAPI.


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