[PATCH 2/4] drm/amdgpu:new method to sync ce&de

[Christian König]

Am 29.08.2016 um 04:55 schrieb Monk Liu:
> CE & DE can have most up to 128dw as the gap between them
> so to sync CE nad DE we don't need double SWITCH_BUFFERs any
> more, which is urgly and harm performance, we only need
> insert 128NOP after VM flush to prevent CE vm fault.
>
> Change-Id: Ibec954ce4c817ad7d3bce89c2bcb95b6c6bb5411
> Signed-off-by: Monk Liu <Monk.Liu at amd.com>

Looks good to me, but only the GFX engines have a CE. So syncing on the 
compute engines is pretty much pointless.

So I suggest that you move this into the "usepfp" if branch as well.

With that fixed the patch is Reviewed-by: Christian König 
<christian.koenig at amd.com>.

Regards,
Christian.

> ---
>   drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c | 18 ++++++------------
>   1 file changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> index 26fced0..ce1e616 100755
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> @@ -6005,14 +6005,6 @@ static void gfx_v8_0_ring_emit_pipeline_sync(struct amdgpu_ring *ring)
>   	amdgpu_ring_write(ring, seq);
>   	amdgpu_ring_write(ring, 0xffffffff);
>   	amdgpu_ring_write(ring, 4); /* poll interval */
> -
> -	if (usepfp) {
> -		/* synce CE with ME to prevent CE fetch CEIB before context switch done */
> -		amdgpu_ring_write(ring, PACKET3(PACKET3_SWITCH_BUFFER, 0));
> -		amdgpu_ring_write(ring, 0);
> -		amdgpu_ring_write(ring, PACKET3(PACKET3_SWITCH_BUFFER, 0));
> -		amdgpu_ring_write(ring, 0);
> -	}
>   }
>   
>   static void gfx_v8_0_ring_emit_vm_flush(struct amdgpu_ring *ring,
> @@ -6020,6 +6012,9 @@ static void gfx_v8_0_ring_emit_vm_flush(struct amdgpu_ring *ring,
>   {
>   	int usepfp = (ring->type == AMDGPU_RING_TYPE_GFX);
>   
> +	/* GFX8 emits 128 dw nop to prevent DE do vm_flush before CE finish CEIB */
> +	amdgpu_ring_insert_nop(ring, 128);
> +
>   	amdgpu_ring_write(ring, PACKET3(PACKET3_WRITE_DATA, 3));
>   	amdgpu_ring_write(ring, (WRITE_DATA_ENGINE_SEL(usepfp) |
>   				 WRITE_DATA_DST_SEL(0)) |
> @@ -6059,11 +6054,10 @@ static void gfx_v8_0_ring_emit_vm_flush(struct amdgpu_ring *ring,
>   		/* sync PFP to ME, otherwise we might get invalid PFP reads */
>   		amdgpu_ring_write(ring, PACKET3(PACKET3_PFP_SYNC_ME, 0));
>   		amdgpu_ring_write(ring, 0x0);
> -		amdgpu_ring_write(ring, PACKET3(PACKET3_SWITCH_BUFFER, 0));
> -		amdgpu_ring_write(ring, 0);
> -		amdgpu_ring_write(ring, PACKET3(PACKET3_SWITCH_BUFFER, 0));
> -		amdgpu_ring_write(ring, 0);
>   	}
> +
> +	/* GFX8 emits 128 dw nop to prevent CE access VM before vm_flush finish */
> +	amdgpu_ring_insert_nop(ring, 128);
>   }
>   
>   static u32 gfx_v8_0_ring_get_rptr_compute(struct amdgpu_ring *ring)