[igt-dev] [PATCH i-g-t 02/17] igt/gem_tiled_partial_pwrite_pread: Check for known swizzling

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-07-05 13:30:57)
> 
> On 05/07/2018 12:14, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2018-07-02 13:00:07)
> >>
> >> On 02/07/2018 10:07, Chris Wilson wrote:
> >>> As we want to compare a templated tiling pattern against the target_bo,
> >>> we need to know that the swizzling is compatible. Or else the two
> >>> tiling pattern may differ due to underlying page address that we cannot
> >>> know, and so the test may sporadically fail.
> >>>
> >>> References: https://bugs.freedesktop.org/show_bug.cgi?id=102575
> >>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >>> ---
> >>>    tests/gem_tiled_partial_pwrite_pread.c | 24 ++++++++++++++++++++++++
> >>>    1 file changed, 24 insertions(+)
> >>>
> >>> diff --git a/tests/gem_tiled_partial_pwrite_pread.c b/tests/gem_tiled_partial_pwrite_pread.c
> >>> index fe573c37c..83c57c07d 100644
> >>> --- a/tests/gem_tiled_partial_pwrite_pread.c
> >>> +++ b/tests/gem_tiled_partial_pwrite_pread.c
> >>> @@ -249,6 +249,24 @@ static void test_partial_read_writes(void)
> >>>        }
> >>>    }
> >>>    
> >>> +static bool known_swizzling(uint32_t handle)
> >>> +{
> >>> +     struct drm_i915_gem_get_tiling2 {
> >>> +             uint32_t handle;
> >>> +             uint32_t tiling_mode;
> >>> +             uint32_t swizzle_mode;
> >>> +             uint32_t phys_swizzle_mode;
> >>> +     } arg = {
> >>> +             .handle = handle,
> >>> +     };
> >>> +#define DRM_IOCTL_I915_GEM_GET_TILING2       DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_GET_TILING, struct
> >>
> >> Can't we rely on this being in system headers by now?
> >>
> >> drm_i915_gem_get_tiling2)
> >>> +
> >>> +     if (igt_ioctl(fd, DRM_IOCTL_I915_GEM_GET_TILING2, &arg))
> >>> +             return false;
> >>> +
> >>> +     return arg.phys_swizzle_mode == arg.swizzle_mode;
> >>> +}
> >>> +
> >>>    igt_main
> >>>    {
> >>>        uint32_t tiling_mode = I915_TILING_X;
> >>> @@ -271,6 +289,12 @@ igt_main
> >>>                                                      &tiling_mode, &scratch_pitch, 0);
> >>>                igt_assert(tiling_mode == I915_TILING_X);
> >>>                igt_assert(scratch_pitch == 4096);
> >>> +
> >>> +             /*
> >>> +              * As we want to compare our template tiled pattern against
> >>> +              * the target bo, we need consistent swizzling on both.
> >>> +              */
> >>> +             igt_require(known_swizzling(scratch_bo->handle));
> >>>                staging_bo = drm_intel_bo_alloc(bufmgr, "staging bo", BO_SIZE, 4096);
> >>>                tiled_staging_bo = drm_intel_bo_alloc_tiled(bufmgr, "scratch bo", 1024,
> >>>                                                            BO_SIZE/4096, 4,
> >>>
> >>
> >> Another option could be to keep allocating until we found one in the
> >> memory area with compatible swizzling? Like this it may be some noise in
> >> the test pass<->skip transitions.
> > 
> > It depends on physical layout which the kernel keeps hidden (for
> > understandable reasons).
> 
> Yeah, but we could allocate more and more until we end up in the area 
> where args.phys_swizzle_mode == args.swizzle_mode. Might be to heavy 
> approach. But then this skip can be random depending on what physical 
> memory gets allocated in each test run.

Ah, but phys_swizzle_mode and swizzle_mode are invariants determined
during boot for each fence-tiling type.
-Chris