On Sun, Oct 11, 2020 at 07:09:49PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> Any cross-device sync use-cases *must* use explicit sync. And if there
> is only a single ring (no-preemption), everything is FIFO order and
> there is no need to implicit-sync.
>
> Mesa should probably just always use MSM_SUBMIT_NO_IMPLICIT, as behavior
> is undefined when fences are not used to synchronize buffer usage across
> contexts (which is the only case where multiple different priority rings
> could come into play).
Uh does this mean msm is broken on dri2/3 and wayland? Or I'm I just
confused by your commit message?
Since for these protocols we do expect implicit sync accross processes to
work. Even across devices (and nvidia have actually provided quite a bunch
of patches to make this work in i915 - ttm based drivers get this right,
plus dumb scanout drivers using the right helpers also get this all
right).
-Daniel
>
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/msm/msm_gem_submit.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> index 3151a0ca8904..c69803ea53c8 100644
> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> @@ -277,7 +277,7 @@ static int submit_lock_objects(struct msm_gem_submit *submit)
> return ret;
> }
>
> -static int submit_fence_sync(struct msm_gem_submit *submit, bool no_implicit)
> +static int submit_fence_sync(struct msm_gem_submit *submit, bool implicit_sync)
> {
> int i, ret = 0;
>
> @@ -297,7 +297,7 @@ static int submit_fence_sync(struct msm_gem_submit *submit, bool no_implicit)
> return ret;
> }
>
> - if (no_implicit)
> + if (!implicit_sync)
> continue;
>
> ret = msm_gem_sync_object(&msm_obj->base, submit->ring->fctx,
> @@ -768,7 +768,8 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
> if (ret)
> goto out;
>
> - ret = submit_fence_sync(submit, !!(args->flags & MSM_SUBMIT_NO_IMPLICIT));
> + ret = submit_fence_sync(submit, (gpu->nr_rings > 1) &&
> + !(args->flags & MSM_SUBMIT_NO_IMPLICIT));
> if (ret)
> goto out;
>
> --
> 2.26.2
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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