Sorry for replying to myself again.
On Wednesday, January 22, 2020 4:24:49 PM CET Janusz Krzysztofik wrote:
> Hi Chris,
>
> On Thursday, January 9, 2020 4:03:30 PM CET Chris Wilson wrote:
> > Quoting Janusz Krzysztofik (2020-01-09 14:01:25)
> > > On future hardware with missing GGTT BAR we won't be able to exercise
> > > dma-buf access via that path. An alternative to basic-gtt subtest for
> > > testing dma-buf access is required, as well as basic-fence-mmap and
> > > coherency-gtt subtest alternatives for testing WC coherency.
> > >
> > > Access to the dma sg list feature exposed by dma-buf can be tested
> > > through blitter. Unfortunately we don't have any equivalently simple
> > > tests that use blitter. Provide them.
> > >
> > > Blitter XY_SRC_COPY method implemented by igt_blitter_src_copy__raw()
> > > IGT library function has been chosen.
> > >
> > > v2: As fast copy is not supported on platforms older than Gen 9,
> > > use XY_SRC_COPY instead (Chris),
> > > - add subtest descriptions.
> > >
> > > Suggested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > Suggested-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxxxxxxxx>
> > > ---
> > > tests/prime_vgem.c | 192 +++++++++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 192 insertions(+)
> > >
> > > diff --git a/tests/prime_vgem.c b/tests/prime_vgem.c
> > > index 69ae8c9b..9ceee47a 100644
> > > --- a/tests/prime_vgem.c
> > > +++ b/tests/prime_vgem.c
> <SNIP>
> > >
> > > +static void test_blt(int vgem, int i915)
> > > +{
> > > + struct vgem_bo scratch;
> > > + uint32_t prime, native;
> > > + uint32_t *ptr;
> > > + int dmabuf, i;
> > > +
> > > + scratch.width = 1024;
> > > + scratch.height = 1024;
> > > + scratch.bpp = 32;
> > > + vgem_create(vgem, &scratch);
> > > +
> > > + dmabuf = prime_handle_to_fd(vgem, scratch.handle);
> > > + prime = prime_fd_to_handle(i915, dmabuf);
> > > + close(dmabuf);
> > > +
> > > + native = gem_create(i915, scratch.size);
> > > +
> > > + ptr = gem_mmap__wc(i915, native, 0, scratch.size, PROT_WRITE);
> > > + for (i = 0; i < 1024; i++)
> > > + ptr[1024 * i] = i;
> > > + munmap(ptr, scratch.size);
> > > +
> > > + igt_blitter_src_copy__raw(i915,
> > > + native, 0, scratch.width * scratch.bpp / 8,
> > > + I915_TILING_NONE, 0, 0,
> > > + scratch.width, scratch.height, scratch.bpp,
> > > + prime, 0, scratch.width * scratch.bpp / 8,
> > > + I915_TILING_NONE, 0, 0);
> > > + gem_sync(i915, prime);
> >
> > Would this be better with prime_sync_start(dmabuf, true); ?
>
> I'm not sure why you suggest true for write access, not false for just having
> the prime object confirmed ready for reading. Could you please explain?
Now I think that by requesting a write sync, as suggested by Chris, we make
sure that all former write operations have completed. That might be not true
if we requested a read sync as we might get a snapshot taken while the write
we wanted to serialize against was still pending. I hope my understanding of
this is now correct.
Thanks,
Janusz
>
> Thanks,
> Janusz
>
> > gem_sync(prime) is nice in its own way (checking sync on imported handle
> > provides correct serialisation for the vgem_mmap). But I think the
> > recommended practice would be to use dmabuf for the inter-device sync?
>
>
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