[PATCH v1 3/3] drm/amdgpu: optimize the padding for gfx_v9_4_3

[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_4_3.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c
> index 98fe6c40da64..c4832a5725c3 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_4_3.c
> @@ -4178,6 +4178,24 @@ static void gfx_v9_4_3_enable_watchdog_timer(struct amdgpu_device *adev)
>         amdgpu_gfx_ras_error_func(adev, NULL, gfx_v9_4_3_inst_enable_watchdog_timer);
>  }
>
> +static void gfx_v9_4_3_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 const struct amd_ip_funcs gfx_v9_4_3_ip_funcs = {
>         .name = "gfx_v9_4_3",
>         .early_init = gfx_v9_4_3_early_init,
> @@ -4227,7 +4245,7 @@ static const struct amdgpu_ring_funcs gfx_v9_4_3_ring_funcs_compute = {
>         .emit_hdp_flush = gfx_v9_4_3_ring_emit_hdp_flush,
>         .test_ring = gfx_v9_4_3_ring_test_ring,
>         .test_ib = gfx_v9_4_3_ring_test_ib,
> -       .insert_nop = amdgpu_ring_insert_nop,
> +       .insert_nop = gfx_v9_4_3_ring_insert_nop,
>         .pad_ib = amdgpu_ring_generic_pad_ib,
>         .emit_wreg = gfx_v9_4_3_ring_emit_wreg,
>         .emit_reg_wait = gfx_v9_4_3_ring_emit_reg_wait,
> --
> 2.34.1
>