[Mesa-stable] [Mesa-dev] [PATCH] i965: Fix brw_render_cache_set_check_flush's PIPE_CONTROLs.

[Jason Ekstrand]

On Mar 26, 2016 12:55 AM, "Kenneth Graunke" <kenneth at whitecape.org> wrote:
>
> Our driver uses the brw_render_cache mechanism to track buffers we've
> rendered to and are about to sample from.
>
> Previously, we did a single PIPE_CONTROL with the following bits set:
> - Render Target Flush
> - Depth Cache Flush
> - Texture Cache Invalidate
> - VF Cache Invalidate
> - Instruction Cache Invalidate
> - CS Stall
>
> This combined both "top of pipe" invalidations and "bottom of pipe"
> flushes, which isn't how the hardware is intended to be programmed.
>
> The "top of pipe" invalidations may happen right away, without any
> guarantees that rendering using those caches has completed.  That
> rendering may continue altering the caches.  The "bottom of pipe"
> flushes do wait for the rendering to complete.  The CS stall also
> prevents further work from happening until data is flushed out.
>
> What we wanted to do was wait for rendering complete, flush the new
> data out of the render and depth caches, wait, then invalidate any
> stale data in read-only caches.  We can accomplish this by doing the
> "bottom of pipe" flushes with a CS stall, then the "top of pipe"
> flushes as a second PIPE_CONTROL.  The flushes will wait until the
> rendering is complete, and the CS stall will prevent the second
> PIPE_CONTROL with the invalidations from executing until the first
> is done.
>
> Fixes dEQP-GLES3.functional.texture.specification.teximage2d_pbo
> subtests on Braswell and Skylake.  These tests hit the meta PBO
> texture upload path, which binds the PBO as a texture and samples
> from it, while rendering to the destination texture.  The tests
> then sample from the texture.
>
> For now, we leave Gen4-5 alone.  It probably needs work too, but
> apparently it hasn't even been setting the (G45+) TC invalidation
> bit at all...

This all seems reasonable.  Assuming Jenkins is happy,

Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

> Cc: mesa-stable at lists.freedesktop.org
> Suggested-by: Francisco Jerez <currojerez at riseup.net>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/brw_pipe_control.c |  2 --
>  src/mesa/drivers/dri/i965/intel_fbo.c        | 15 ++++++++++++++-
>  2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_pipe_control.c
b/src/mesa/drivers/dri/i965/brw_pipe_control.c
> index b41e28e..4672efd 100644
> --- a/src/mesa/drivers/dri/i965/brw_pipe_control.c
> +++ b/src/mesa/drivers/dri/i965/brw_pipe_control.c
> @@ -338,8 +338,6 @@ brw_emit_mi_flush(struct brw_context *brw)
>        }
>        brw_emit_pipe_control_flush(brw, flags);
>     }
> -
> -   brw_render_cache_set_clear(brw);
>  }
>
>  int
> diff --git a/src/mesa/drivers/dri/i965/intel_fbo.c
b/src/mesa/drivers/dri/i965/intel_fbo.c
> index b7b6796..707041a 100644
> --- a/src/mesa/drivers/dri/i965/intel_fbo.c
> +++ b/src/mesa/drivers/dri/i965/intel_fbo.c
> @@ -1065,7 +1065,20 @@ brw_render_cache_set_check_flush(struct
brw_context *brw, drm_intel_bo *bo)
>     if (!_mesa_set_search(brw->render_cache, bo))
>        return;
>
> -   brw_emit_mi_flush(brw);
> +   if (brw->gen >= 6) {
> +      brw_emit_pipe_control_flush(brw,
> +                                  PIPE_CONTROL_DEPTH_CACHE_FLUSH |
> +                                  PIPE_CONTROL_RENDER_TARGET_FLUSH |
> +                                  PIPE_CONTROL_CS_STALL);
> +
> +      brw_emit_pipe_control_flush(brw,
> +                                  PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE |
> +                                  PIPE_CONTROL_CONST_CACHE_INVALIDATE);
> +   } else {
> +      brw_emit_mi_flush(brw);
> +   }
> +
> +   brw_render_cache_set_clear(brw);
>  }
>
>  /**
> --
> 2.7.3
>
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