[Intel-gfx] [PATCH 2/2] drm/i915: Bump pin_count to UINT_MAX.

[Maarten Lankhorst]

Op 23-05-16 om 17:43 schreef Chris Wilson:
> On Mon, May 23, 2016 at 05:09:05PM +0200, Maarten Lankhorst wrote:
>> Op 23-05-16 om 16:25 schreef Chris Wilson:
>>> On Mon, May 23, 2016 at 03:37:41PM +0200, Maarten Lankhorst wrote:
>>>> With nonblocking unpin there can be many cursor pins before they're
>>>> cleared by the next page flip.
>>>>
>>>> Fix this by extending pin_count to the full 32-bit to prevent a
>>>> WARN_ON(vma->pin_count == DRM_I915_GEM_OBJECT_MAX_PIN_COUNT)
>>> This is a hack that affects non-KMS paths. Being able to process binding
>>> in a single operation on all architectures is something we want to
>>> preserve.
>>>
>>> Why is every cursor movement generating an unpin work? Should I just
>>> start poking registers from userspace to avoid a silly kerenl?
>>> -Chris
>>>
>> All the unpin work gets batched till after the next vblank, it's not very efficient
>> but if you want to fix it you should just add the vma to plane state already.
> I still don't see where the flush will occur, or why vblanks would be
> running at all for cursor updates.
Next page flip. All cursor updates are added to flip_work list and are cleared on vblank.
>> According to Ville unpin count would still be too low on BXT/SKL, so it wouldn't
>> remove the need for this patch anyway..
> Increasing the count is one thing, taking all 32bits as a workaround for
> poor behaviour in the cursor update is another.
> -Chris
>