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

[Felix Kuehling]

Am 2021-05-25 um 1:56 p.m. 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;

I wonder if this check should be inside hdp_v4_0_flush_hdp instead so it
catches all unnecessary HDP flushing. On the other hand, that would
still leave the mb(). But that mb() is probably needed anyway to ensure
that the GPU will see any previous memory writes.

Regards,
  Felix


>         /* Flush HDP */
>         mb();
>         amdgpu_asic_flush_hdp(p->adev, NULL);
> _______________________________________________
> amd-gfx mailing list
> amd-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx