[Intel-gfx] [PATCH 2/2] drm/i915/lrc: Skip no-op per-bb buffer on gen9

[Tvrtko Ursulin]

On 21/09/2017 14:54, Chris Wilson wrote:
> Since we inherited the context image setup from gen8 which needed a
> per-bb workaround (for GPGPU), we are submitting an empty per-bb buffer
> on gen9. Now that we can skip adding the buffer to the context image,
> remove the dangling per-bb. This slightly improves execution latency,
> most notably on an idle engine.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=87725

How much of the 7% we get back? :)

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   drivers/gpu/drm/i915/intel_lrc.c | 9 +--------
>   1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 297c9c1564e5..91a5411bb9da 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1171,13 +1171,6 @@ static u32 *gen9_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
>   	return batch;
>   }
>   
> -static u32 *gen9_init_perctx_bb(struct intel_engine_cs *engine, u32 *batch)
> -{
> -	*batch++ = MI_BATCH_BUFFER_END;
> -
> -	return batch;
> -}
> -
>   #define CTX_WA_BB_OBJ_SIZE (PAGE_SIZE)
>   
>   static int lrc_setup_wa_ctx(struct intel_engine_cs *engine)
> @@ -1234,7 +1227,7 @@ static int intel_init_workaround_bb(struct intel_engine_cs *engine)
>   		return 0;
>   	case 9:
>   		wa_bb_fn[0] = gen9_init_indirectctx_bb;
> -		wa_bb_fn[1] = gen9_init_perctx_bb;
> +		wa_bb_fn[1] = NULL;
>   		break;
>   	case 8:
>   		wa_bb_fn[0] = gen8_init_indirectctx_bb;
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko