[PATCH v1 2/3] drm/amdgpu: optimize the padding for gfx9

[Marek Olšák]

On Wed, Jul 31, 2024 at 9:13 AM Sunil Khatri <sunil.khatri at amd.com> wrote:
>
> Adding NOP packets one by one in the ring
> does not use the CP efficiently.
>
> Solution:
> Use CP optimization while adding NOP packet's so PFP
> can discard NOP packets based on information of count
> from the Header instead of fetching all NOP packets
> one by one.
>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
> Cc: Tvrtko Ursulin <tursulin at igalia.com>
> Cc: Marek Olšák <marek.olsak at amd.com>
> Signed-off-by: Sunil Khatri <sunil.khatri at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 24 +++++++++++++++++++++---
>  1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 675a1a8e2515..991f7c2fc1a2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -7100,6 +7100,24 @@ static void gfx_v9_0_emit_wave_limit(struct amdgpu_ring *ring, bool enable)
>         }
>  }
>
> +static void gfx_v9_ring_insert_nop(struct amdgpu_ring *ring, uint32_t num_nop)
> +{
> +       int i;
> +
> +       /* Header itself is a NOP packet */
> +       if (num_nop == 1) {
> +               amdgpu_ring_write(ring, ring->funcs->nop);
> +               return;
> +       }
> +
> +       /* Max HW optimization till 0x3ffe, followed by remaining one NOP at a time*/
> +       amdgpu_ring_write(ring, PACKET3(PACKET3_NOP, min(num_nop - 2, 0x3ffe)));
> +
> +       /* Header is at index 0, followed by num_nops - 1 NOP packet's */
> +       for (i = 1; i < num_nop; i++)
> +               amdgpu_ring_write(ring, ring->funcs->nop);

This loop should be removed. I explained the reason in the gfx10 commit.

Marek

> +}
> +
>  static void gfx_v9_ip_print(void *handle, struct drm_printer *p)
>  {
>         struct amdgpu_device *adev = (struct amdgpu_device *)handle;
> @@ -7240,7 +7258,7 @@ static const struct amdgpu_ring_funcs gfx_v9_0_ring_funcs_gfx = {
>         .emit_gds_switch = gfx_v9_0_ring_emit_gds_switch,
>         .emit_hdp_flush = gfx_v9_0_ring_emit_hdp_flush,
>         .test_ring = gfx_v9_0_ring_test_ring,
> -       .insert_nop = amdgpu_ring_insert_nop,
> +       .insert_nop = gfx_v9_ring_insert_nop,
>         .pad_ib = amdgpu_ring_generic_pad_ib,
>         .emit_switch_buffer = gfx_v9_ring_emit_sb,
>         .emit_cntxcntl = gfx_v9_ring_emit_cntxcntl,
> @@ -7294,7 +7312,7 @@ static const struct amdgpu_ring_funcs gfx_v9_0_sw_ring_funcs_gfx = {
>         .emit_hdp_flush = gfx_v9_0_ring_emit_hdp_flush,
>         .test_ring = gfx_v9_0_ring_test_ring,
>         .test_ib = gfx_v9_0_ring_test_ib,
> -       .insert_nop = amdgpu_sw_ring_insert_nop,
> +       .insert_nop = gfx_v9_ring_insert_nop,
>         .pad_ib = amdgpu_ring_generic_pad_ib,
>         .emit_switch_buffer = gfx_v9_ring_emit_sb,
>         .emit_cntxcntl = gfx_v9_ring_emit_cntxcntl,
> @@ -7338,7 +7356,7 @@ static const struct amdgpu_ring_funcs gfx_v9_0_ring_funcs_compute = {
>         .emit_hdp_flush = gfx_v9_0_ring_emit_hdp_flush,
>         .test_ring = gfx_v9_0_ring_test_ring,
>         .test_ib = gfx_v9_0_ring_test_ib,
> -       .insert_nop = amdgpu_ring_insert_nop,
> +       .insert_nop = gfx_v9_ring_insert_nop,
>         .pad_ib = amdgpu_ring_generic_pad_ib,
>         .emit_wreg = gfx_v9_0_ring_emit_wreg,
>         .emit_reg_wait = gfx_v9_0_ring_emit_reg_wait,
> --
> 2.34.1
>