[Intel-gfx] [PATCH] drm/amdgpu: Transfer fences to dmabuf importer

[Chris Wilson]

Quoting Huang Rui (2018-08-07 11:56:24)
> On Tue, Aug 07, 2018 at 11:45:00AM +0100, Chris Wilson wrote:
> > amdgpu only uses shared-fences internally, but dmabuf importers rely on
> > implicit write hazard tracking via the reservation_object.fence_excl.
> > For example, the importer use the write hazard for timing a page flip to
> > only occur after the exporter has finished flushing its write into the
> > surface. As such, on exporting a dmabuf, we must either flush all
> > outstanding fences (for we do not know which are writes and should have
> > been exclusive) or alternatively create a new exclusive fence that is
> > the composite of all the existing shared fences, and so will only be
> > signaled when all earlier fences are signaled (ensuring that we can not
> > be signaled before the completion of any earlier write).
> > 
> > Testcase: igt/amd_prime/amd-to-i915
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Alex Deucher <alexander.deucher at amd.com>
> > Cc: "Christian König" <christian.koenig at amd.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c | 70 ++++++++++++++++++++---
> >  1 file changed, 62 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> > index 1c5d97f4b4dd..47e6ec5510b6 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> > @@ -37,6 +37,7 @@
> >  #include "amdgpu_display.h"
> >  #include <drm/amdgpu_drm.h>
> >  #include <linux/dma-buf.h>
> > +#include <linux/dma-fence-array.h>
> >  
> >  static const struct dma_buf_ops amdgpu_dmabuf_ops;
> >  
> > @@ -188,6 +189,57 @@ amdgpu_gem_prime_import_sg_table(struct drm_device *dev,
> >       return ERR_PTR(ret);
> >  }
> >  
> > +static int
> > +__reservation_object_make_exclusive(struct reservation_object *obj)
> > +{
> 
> Why not you move the helper to reservation.c, and then export symbol for
> this file?

I have not seen anything else that would wish to use this helper. The
first task is to solve this issue here before worrying about
generalisation.
-Chris