Re: [PATCH v2 5/5] drm/vc4: Expose dma-buf fences for V3D rendering.

[Eric Anholt <eric@anholt.net>]

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Daniel Vetter <daniel@ffwll.ch> writes:

> On Wed, Apr 12, 2017 at 12:12:02PM -0700, Eric Anholt wrote:
>> This is needed for proper synchronization with display on another DRM
>> device (pl111 or tinydrm) with buffers produced by vc4 V3D.  Fixes the
>> new igt vc4_dmabuf_poll testcase, and rendering of one of the glmark2
>> desktop tests on pl111+vc4.
>> 
>> This doesn't yet introduce waits on other device's fences before vc4's
>> rendering/display, because I don't have testcases for them.
>> 
>> v2: Reuse dma_fence_free(), retitle commit message to clarify that
>>     it's not a full dma-buf fencing implementation yet.
>> 
>> Signed-off-by: Eric Anholt <eric@anholt.net>
>
> Double-checked a few things in your ww_mutex scheme, seems are correct.
> And testing with CONFIG_DEBUG_WW_MUTEX_SLOWPATH should catch any kind of
> fumbles in your error paths. I didnt do a full review, so just

Yeah, the lockdep and WW debug options were incredibly useful (and I
should probably go turn them off now).

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