[Mesa-dev] [PATCH] r600g: pad IBs to a multiple of 4 DWs on r6xx

[Dominik Behr]

0x80000000 is Type 2 NOP.
You could make it a little better/faster by inserting single multi-DWORD
Type 3 NOP
And pad to 8 DWORDs. CP fetches are 32 bytes each and R600 has requires
padding. Same with padding CP ring buffer updates to 32 bytes (pad to
32bytes before you update CP_RB_WPTR).


On Thu, Sep 5, 2013 at 3:56 PM, Marek Olšák <maraeo at gmail.com> wrote:

> Reviewed-by: Marek Olšák <marek.olsak at amd.com>
>
> Though I'm not sure if 0x80000000 is correct.
>
> Marek
>
> On Wed, Sep 4, 2013 at 11:55 PM, Alex Deucher <alexdeucher at gmail.com>
> wrote:
> > IBs need to be a multiple of 4 dwords on r6xx asics
> > to avoid a hw bug.
> >
> > Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> > CC: "9.2" <mesa-stable at lists.freedesktop.org>
> > CC: "9.1" <mesa-stable at lists.freedesktop.org>
> > ---
> >  src/gallium/drivers/r600/r600_hw_context.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/src/gallium/drivers/r600/r600_hw_context.c
> b/src/gallium/drivers/r600/r600_hw_context.c
> > index 97b0f9c..0a219af 100644
> > --- a/src/gallium/drivers/r600/r600_hw_context.c
> > +++ b/src/gallium/drivers/r600/r600_hw_context.c
> > @@ -347,6 +347,19 @@ void r600_context_flush(struct r600_context *ctx,
> unsigned flags)
> >                 flags |= RADEON_FLUSH_KEEP_TILING_FLAGS;
> >         }
> >
> > +       /* Pad the GFX CS to a multiple of 4 dwords on rv6xx
> > +        * to avoid a hw bug.
> > +        */
> > +       if (ctx->chip_class < R700) {
> > +               unsigned i;
> > +               unsigned padding_dw = 4 - cs->cdw % 4;
> > +               if (padding_dw < 4) {
> > +                       for (i = 0; i < padding_dw; i++) {
> > +                               cs->buf[cs->cdw++] = 0x80000000;
> > +                       }
> > +               }
> > +       }
> > +
> >         /* Flush the CS. */
> >         ctx->ws->cs_flush(ctx->rings.gfx.cs, flags,
> ctx->screen->cs_count++);
> >  }
> > --
> > 1.8.3.1
> >
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