[PATCH] drm/amdgpu: optimize to drop preamble IB for old GPUs

[Christian König]

Well NAK, as discussed checking the global flag is more flexible since 
it will still enable the preamble drop when gfxoff is disabled.

Christian.

Am 17.05.21 um 06:39 schrieb Jiansong Chen:
> The optimization is safe for old GPUs and can help performance.
>
> Signed-off-by: Jiansong Chen <Jiansong.Chen at amd.com>
> Change-Id: Id3b1250f1fe46dddbe8498894fb97e9753b7cafe
> ---
>   drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c | 6 ++++++
>   drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c | 6 ++++++
>   2 files changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c
> index 3a8d52a54873..c915cc439484 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c
> @@ -1873,6 +1873,12 @@ static void gfx_v6_0_ring_emit_ib(struct amdgpu_ring *ring,
>   		amdgpu_ring_write(ring, 0);
>   	}
>   
> +	/* drop the CE preamble IB for the same context */
> +	if ((ib->flags & AMDGPU_IB_FLAG_PREAMBLE) &&
> +	    !(flags & AMDGPU_HAVE_CTX_SWITCH) &&
> +	    !(flags & AMDGPU_PREAMBLE_IB_PRESENT_FIRST))
> +		return;
> +
>   	if (ib->flags & AMDGPU_IB_FLAG_CE)
>   		header = PACKET3(PACKET3_INDIRECT_BUFFER_CONST, 2);
>   	else
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c
> index c35fdd2ef2d4..6d9ccae48024 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c
> @@ -2269,6 +2269,12 @@ static void gfx_v7_0_ring_emit_ib_gfx(struct amdgpu_ring *ring,
>   		amdgpu_ring_write(ring, 0);
>   	}
>   
> +	/* drop the CE preamble IB for the same context */
> +	if ((ib->flags & AMDGPU_IB_FLAG_PREAMBLE) &&
> +	    !(flags & AMDGPU_HAVE_CTX_SWITCH) &&
> +	    !(flags & AMDGPU_PREAMBLE_IB_PRESENT_FIRST))
> +		return;
> +
>   	if (ib->flags & AMDGPU_IB_FLAG_CE)
>   		header = PACKET3(PACKET3_INDIRECT_BUFFER_CONST, 2);
>   	else