On Tue, Jul 30, 2024 at 8:43 AM Sunil Khatri <sunil.khatri@xxxxxxx> 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@xxxxxxx>
> Cc: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@xxxxxxx>
> Cc: Tvrtko Ursulin <tursulin@xxxxxxxxxx>
> Cc: Marek Olšák <marek.olsak@xxxxxxx>
> Signed-off-by: Sunil Khatri <sunil.khatri@xxxxxxx>
> ---
> drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c | 24 +++++++++++++++++++++---
> 1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> index 853084a2ce7f..edf5b5c4d185 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> @@ -9397,6 +9397,24 @@ static void gfx_v10_0_emit_mem_sync(struct amdgpu_ring *ring)
> amdgpu_ring_write(ring, gcr_cntl); /* GCR_CNTL */
> }
>
> +static void amdgpu_gfx10_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. It's unnecessary CPU overhead and we
should never get more than 0x3fff NOPs (maybe use BUG_ON). Leaving the
whole packet body uninitialized is the fastest option.
Marek
> +}
> +
> static void gfx_v10_ip_print(void *handle, struct drm_printer *p)
> {
> struct amdgpu_device *adev = (struct amdgpu_device *)handle;
> @@ -9588,7 +9606,7 @@ static const struct amdgpu_ring_funcs gfx_v10_0_ring_funcs_gfx = {
> .emit_hdp_flush = gfx_v10_0_ring_emit_hdp_flush,
> .test_ring = gfx_v10_0_ring_test_ring,
> .test_ib = gfx_v10_0_ring_test_ib,
> - .insert_nop = amdgpu_ring_insert_nop,
> + .insert_nop = amdgpu_gfx10_ring_insert_nop,
> .pad_ib = amdgpu_ring_generic_pad_ib,
> .emit_switch_buffer = gfx_v10_0_ring_emit_sb,
> .emit_cntxcntl = gfx_v10_0_ring_emit_cntxcntl,
> @@ -9629,7 +9647,7 @@ static const struct amdgpu_ring_funcs gfx_v10_0_ring_funcs_compute = {
> .emit_hdp_flush = gfx_v10_0_ring_emit_hdp_flush,
> .test_ring = gfx_v10_0_ring_test_ring,
> .test_ib = gfx_v10_0_ring_test_ib,
> - .insert_nop = amdgpu_ring_insert_nop,
> + .insert_nop = amdgpu_gfx10_ring_insert_nop,
> .pad_ib = amdgpu_ring_generic_pad_ib,
> .emit_wreg = gfx_v10_0_ring_emit_wreg,
> .emit_reg_wait = gfx_v10_0_ring_emit_reg_wait,
> @@ -9659,7 +9677,7 @@ static const struct amdgpu_ring_funcs gfx_v10_0_ring_funcs_kiq = {
> .emit_fence = gfx_v10_0_ring_emit_fence_kiq,
> .test_ring = gfx_v10_0_ring_test_ring,
> .test_ib = gfx_v10_0_ring_test_ib,
> - .insert_nop = amdgpu_ring_insert_nop,
> + .insert_nop = amdgpu_gfx10_ring_insert_nop,
> .pad_ib = amdgpu_ring_generic_pad_ib,
> .emit_rreg = gfx_v10_0_ring_emit_rreg,
> .emit_wreg = gfx_v10_0_ring_emit_wreg,
> --
> 2.34.1
>
