[Mesa-dev] [PATCH] i965: Upload invariant state once at the start of the batch on Gen4-5.

[Jason Ekstrand]

Sounds like a plan.

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

On Thu, Nov 16, 2017 at 12:37 AM, Kenneth Graunke <kenneth at whitecape.org>
wrote:

> We want to emit invariant state at the start of a render batch.  In the
> past, this more or less happened: a new batch flagged BRW_NEW_CONTEXT
> (because we don't have hardware contexts), which triggered the
> brw_invariant_state atom.  So, it would be emitted before any 3D
> drawing.  (Technically, there might be some BLT commands in the batch
> because Gen4-5 have a single combined render/BLT ring, but that should
> be harmless).
>
> With the advent of BLORP, this broke.  The first item in a batch might
> be a BLORP operation, which bypasses the normal draw upload path.  So,
> we need to ensure invariant state happens first.  To do that, we just
> upload it when creating a new batch.  On Gen6+ we'd need to worry about
> whether it's a RENDER or BLT batch, but because we have a combined ring,
> this approach should work fine on Gen4-5.
>
> Seems to fix GPU hangs when playing hardware accelerated video with
> mpv -hwdec=vaapi on Ironlake.
>
> Cc: mesa-stable at lists.freedesktop.org
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103529
> ---
>  src/mesa/drivers/dri/i965/brw_misc_state.c    | 9 ---------
>  src/mesa/drivers/dri/i965/brw_state.h         | 1 -
>  src/mesa/drivers/dri/i965/genX_state_upload.c | 2 --
>  src/mesa/drivers/dri/i965/intel_batchbuffer.c | 4 +++-
>  4 files changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_misc_state.c
> b/src/mesa/drivers/dri/i965/brw_misc_state.c
> index fd96485d574..94d5c9783db 100644
> --- a/src/mesa/drivers/dri/i965/brw_misc_state.c
> +++ b/src/mesa/drivers/dri/i965/brw_misc_state.c
> @@ -560,15 +560,6 @@ brw_upload_invariant_state(struct brw_context *brw)
>     ADVANCE_BATCH();
>  }
>
> -const struct brw_tracked_state brw_invariant_state = {
> -   .dirty = {
> -      .mesa = 0,
> -      .brw = BRW_NEW_BLORP |
> -             BRW_NEW_CONTEXT,
> -   },
> -   .emit = brw_upload_invariant_state
> -};
> -
>  /**
>   * Define the base addresses which some state is referenced from.
>   *
> diff --git a/src/mesa/drivers/dri/i965/brw_state.h
> b/src/mesa/drivers/dri/i965/brw_state.h
> index cf13eca3438..ad508950f78 100644
> --- a/src/mesa/drivers/dri/i965/brw_state.h
> +++ b/src/mesa/drivers/dri/i965/brw_state.h
> @@ -51,7 +51,6 @@ extern const struct brw_tracked_state
> brw_wm_pull_constants;
>  extern const struct brw_tracked_state brw_cs_pull_constants;
>  extern const struct brw_tracked_state brw_constant_buffer;
>  extern const struct brw_tracked_state brw_curbe_offsets;
> -extern const struct brw_tracked_state brw_invariant_state;
>  extern const struct brw_tracked_state brw_binding_table_pointers;
>  extern const struct brw_tracked_state brw_depthbuffer;
>  extern const struct brw_tracked_state brw_recalculate_urb_fence;
> diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c
> b/src/mesa/drivers/dri/i965/genX_state_upload.c
> index d4b0de850c9..112f48181b0 100644
> --- a/src/mesa/drivers/dri/i965/genX_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/genX_state_upload.c
> @@ -5366,8 +5366,6 @@ genX(init_atoms)(struct brw_context *brw)
>
>        /* Command packets:
>         */
> -      &brw_invariant_state,
> -
>        &brw_binding_table_pointers,
>        &genX(blend_constant_color),
>
> diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> index bbe13f34cef..3412b1d0a5f 100644
> --- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> +++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> @@ -601,8 +601,10 @@ brw_new_batch(struct brw_context *brw)
>      * would otherwise be stored in the context (which for all intents and
>      * purposes means everything).
>      */
> -   if (brw->hw_ctx == 0)
> +   if (brw->hw_ctx == 0) {
>        brw->ctx.NewDriverState |= BRW_NEW_CONTEXT;
> +      brw_upload_invariant_state(brw);
> +   }
>
>     brw->ctx.NewDriverState |= BRW_NEW_BATCH;
>
> --
> 2.15.0
>
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