[PATCH] drm/amdgpu: Don't flush HDP on A+A

[Christian König]

Am 25.05.21 um 19:56 schrieb Eric Huang:
> With XGMI connection flushing HDP on PCIe is unnecessary,
> it is also to optimize memory allocation latency.
>
> Signed-off-by: Eric Huang <jinhuieric.huang at amd.com>
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_cpu.c 
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_cpu.c
> index ac45d9c7a4e9..aefb3d2927d5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_cpu.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_cpu.c
> @@ -108,6 +108,8 @@ static int amdgpu_vm_cpu_update(struct 
> amdgpu_vm_update_params *p,
>  static int amdgpu_vm_cpu_commit(struct amdgpu_vm_update_params *p,
>                                 struct dma_fence **fence)
>  {
> +       if (p->adev->gmc.xgmi.connected_to_cpu)
> +               return 0;

You still need at least the memory barrier and I suggest to add a common 
flag/function to check if HDP flushing is needed or not.

We also have a bunch of cases in the IB submission code as well.

Christian.

>         /* Flush HDP */
>         mb();
>         amdgpu_asic_flush_hdp(p->adev, NULL);
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