Re: [igt-dev] [PATCH i-g-t v3 1/2] lib/igt_fb: Don't use blitter for large buffers

Chris Wilson
2019-04-08T17:20:56Z

Quoting Chris Wilson (2019-04-08 18:19:26)
> Quoting Ville Syrjala (2019-04-08 18:13:06)
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > The blitter stride is limited to <32k. Fall back to gtt mmap or
> > rendercopy if we're about to exceed that.
> >
> > Not quite sure why we're not just using gtt mmap for Y tiling
> > always. But let's keep it like that for now.
> >
> > v2: Use rendercopy as the fallback for Yf
> > v3: Deal with gen4+ tiled stride correctly (Chris)
> >
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > lib/igt_fb.c | 36 +++++++++++++++++++++++++++++-------
> > 1 file changed, 29 insertions(+), 7 deletions(-)
> >
> > diff --git a/lib/igt_fb.c b/lib/igt_fb.c
> > index 6adf422228e8..d2f756dba2e9 100644
> > --- a/lib/igt_fb.c
> > +++ b/lib/igt_fb.c
> > @@ -1576,6 +1576,31 @@ struct fb_blit_upload {
> > struct intel_batchbuffer *batch;
> > };
> >
> > +static int max_blitter_stride(int fd, uint64_t modifier)
> > +{
> > + int stride = 32768;
> > +
> > + if (intel_gen(intel_get_drm_devid(fd)) >= 4 &&
> > + modifier != DRM_FORMAT_MOD_NONE)
>
> * fingers crossed that the modifier is the single truth
>
> > + stride *= 4;
> > +
> > + return stride;
> > +}
> > +
> > +static bool use_rendercopy(const struct igt_fb *fb)
> > +{
> > + return is_ccs_modifier(fb->modifier) ||
> > + (fb->modifier == I915_FORMAT_MOD_Yf_TILED &&
> > + fb->strides[0] >= max_blitter_stride(fb->fd, fb->modifier));
> > +}
> > +
> > +static bool use_blitter(const struct igt_fb *fb)
> > +{
> > + return (fb->modifier == I915_FORMAT_MOD_Y_TILED ||
> > + fb->modifier == I915_FORMAT_MOD_Yf_TILED) &&

Oh but you would prefer to use rendercopy for Y_TILED (not just
Yf_TILED). The blitter does work with Y_TILED, but it is quite slow.
-Chris