[PATCH] drm/amdgpu: disable ring_muxer if mcbp is off

[Alex Deucher]

On Fri, Feb 23, 2024 at 4:48 AM Pierre-Eric Pelloux-Prayer
<pierre-eric.pelloux-prayer at amd.com> wrote:
>
> Using the ring_muxer without preemption adds overhead for no
> reason since mcbp cannot be triggered.
>
> Moving back to a single queue in this case also helps when
> high priority app are used: in this case the gpu_scheduler
> priority handling will work as expected - much better than
> ring_muxer with its 2 independant schedulers competing for
> the same hardware queue.
>
> This change requires moving amdgpu_device_set_mcbp above
> amdgpu_device_ip_early_init because we use adev->gfx.mcbp.
>
> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  4 ++--
>  drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c      | 21 ++++++++++++---------
>  2 files changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index d534e192e260..40516d24026c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4054,13 +4054,13 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>                 return r;
>         }
>
> +       amdgpu_device_set_mcbp(adev);
> +
>         /* early init functions */
>         r = amdgpu_device_ip_early_init(adev);
>         if (r)
>                 return r;
>
> -       amdgpu_device_set_mcbp(adev);
> -
>         /* Get rid of things like offb */
>         r = drm_aperture_remove_conflicting_pci_framebuffers(adev->pdev, &amdgpu_kms_driver);
>         if (r)
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 169d45268ef6..f682f830f7f6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -2080,7 +2080,7 @@ static int gfx_v9_0_sw_init(void *handle)
>                 ring->doorbell_index = adev->doorbell_index.gfx_ring0 << 1;
>
>                 /* disable scheduler on the real ring */
> -               ring->no_scheduler = true;
> +               ring->no_scheduler = adev->gfx.mcbp;
>                 ring->vm_hub = AMDGPU_GFXHUB(0);
>                 r = amdgpu_ring_init(adev, ring, 1024, &adev->gfx.eop_irq,
>                                      AMDGPU_CP_IRQ_GFX_ME0_PIPE0_EOP,
> @@ -2090,7 +2090,7 @@ static int gfx_v9_0_sw_init(void *handle)
>         }
>
>         /* set up the software rings */
> -       if (adev->gfx.num_gfx_rings) {
> +       if (adev->gfx.mcbp && adev->gfx.num_gfx_rings) {
>                 for (i = 0; i < GFX9_NUM_SW_GFX_RINGS; i++) {
>                         ring = &adev->gfx.sw_gfx_ring[i];
>                         ring->ring_obj = NULL;
> @@ -2181,7 +2181,7 @@ static int gfx_v9_0_sw_fini(void *handle)
>         int i;
>         struct amdgpu_device *adev = (struct amdgpu_device *)handle;
>
> -       if (adev->gfx.num_gfx_rings) {
> +       if (adev->gfx.mcbp && adev->gfx.num_gfx_rings) {
>                 for (i = 0; i < GFX9_NUM_SW_GFX_RINGS; i++)
>                         amdgpu_ring_fini(&adev->gfx.sw_gfx_ring[i]);
>                 amdgpu_ring_mux_fini(&adev->gfx.muxer);
> @@ -5910,11 +5910,14 @@ static int gfx_v9_0_eop_irq(struct amdgpu_device *adev,
>
>         switch (me_id) {
>         case 0:
> -               if (adev->gfx.num_gfx_rings &&
> -                   !amdgpu_mcbp_handle_trailing_fence_irq(&adev->gfx.muxer)) {
> -                       /* Fence signals are handled on the software rings*/
> -                       for (i = 0; i < GFX9_NUM_SW_GFX_RINGS; i++)
> -                               amdgpu_fence_process(&adev->gfx.sw_gfx_ring[i]);
> +               if (adev->gfx.num_gfx_rings) {
> +                       if (!adev->gfx.mcbp) {
> +                               amdgpu_fence_process(&adev->gfx.gfx_ring[0]);
> +                       } else if (!amdgpu_mcbp_handle_trailing_fence_irq(&adev->gfx.muxer)) {
> +                               /* Fence signals are handled on the software rings*/
> +                               for (i = 0; i < GFX9_NUM_SW_GFX_RINGS; i++)
> +                                       amdgpu_fence_process(&adev->gfx.sw_gfx_ring[i]);
> +                       }
>                 }
>                 break;
>         case 1:
> @@ -7051,7 +7054,7 @@ static void gfx_v9_0_set_ring_funcs(struct amdgpu_device *adev)
>         for (i = 0; i < adev->gfx.num_gfx_rings; i++)
>                 adev->gfx.gfx_ring[i].funcs = &gfx_v9_0_ring_funcs_gfx;
>
> -       if (adev->gfx.num_gfx_rings) {
> +       if (adev->gfx.mcbp && adev->gfx.num_gfx_rings) {
>                 for (i = 0; i < GFX9_NUM_SW_GFX_RINGS; i++)
>                         adev->gfx.sw_gfx_ring[i].funcs = &gfx_v9_0_sw_ring_funcs_gfx;
>         }
> --
> 2.40.1
>