[igt-dev] [PATCH i-g-t 2/2] tests/prime_vgem: Examine blitter access path

[Janusz Krzysztofik]

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 at chris-wilson.co.uk>
> > Suggested-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> > ---
> >  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?

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?