[Mesa-dev] [PATCH] radv: make sure CP DMA is idle at the end of IBs

[Bas Nieuwenhuizen]

I'm wondering whether we need to do this more often in pipeline barriers?

Also I'd really appreciate if you could add a check to see if there is
any CP DMA activity in the first place.

On Thu, Jun 21, 2018 at 11:04 AM, Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
> Ported from RadeonSI.
> This might fix some synchronization issues.
>
> I don't know if that will affect performance.
>
> CC: <mesa-stable at lists.freedesktop.org>
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/amd/vulkan/radv_cmd_buffer.c |  6 ++++++
>  src/amd/vulkan/radv_private.h    |  2 ++
>  src/amd/vulkan/si_cmd_buffer.c   | 12 +++++++++++-
>  3 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/src/amd/vulkan/radv_cmd_buffer.c b/src/amd/vulkan/radv_cmd_buffer.c
> index 8bd41bc41ac..a8ab4d3b977 100644
> --- a/src/amd/vulkan/radv_cmd_buffer.c
> +++ b/src/amd/vulkan/radv_cmd_buffer.c
> @@ -2585,6 +2585,12 @@ VkResult radv_EndCommandBuffer(
>                 si_emit_cache_flush(cmd_buffer);
>         }
>
> +       /* Make sure CP DMA is idle at the end of IBs after L2 prefetches
> +        * because the kernel doesn't wait for it.
> +        */
> +       if (cmd_buffer->device->physical_device->rad_info.chip_class >= CIK)
> +               si_cp_dma_wait_for_idle(cmd_buffer);
> +
>         vk_free(&cmd_buffer->pool->alloc, cmd_buffer->state.attachments);
>
>         if (!cmd_buffer->device->ws->cs_finalize(cmd_buffer->cs))
> diff --git a/src/amd/vulkan/radv_private.h b/src/amd/vulkan/radv_private.h
> index c77a8b297f8..b0ecb626d4c 100644
> --- a/src/amd/vulkan/radv_private.h
> +++ b/src/amd/vulkan/radv_private.h
> @@ -1088,6 +1088,8 @@ void si_cp_dma_prefetch(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
>                          unsigned size);
>  void si_cp_dma_clear_buffer(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
>                             uint64_t size, unsigned value);
> +void si_cp_dma_wait_for_idle(struct radv_cmd_buffer *cmd_buffer);
> +
>  void radv_set_db_count_control(struct radv_cmd_buffer *cmd_buffer);
>  bool
>  radv_cmd_buffer_upload_alloc(struct radv_cmd_buffer *cmd_buffer,
> diff --git a/src/amd/vulkan/si_cmd_buffer.c b/src/amd/vulkan/si_cmd_buffer.c
> index e350bccae33..a5ee79a9e72 100644
> --- a/src/amd/vulkan/si_cmd_buffer.c
> +++ b/src/amd/vulkan/si_cmd_buffer.c
> @@ -1034,7 +1034,6 @@ static void si_emit_cp_dma(struct radv_cmd_buffer *cmd_buffer,
>         struct radeon_cmdbuf *cs = cmd_buffer->cs;
>         uint32_t header = 0, command = 0;
>
> -       assert(size);
>         assert(size <= cp_dma_max_byte_count(cmd_buffer));
>
>         radeon_check_space(cmd_buffer->device->ws, cmd_buffer->cs, 9);
> @@ -1237,6 +1236,17 @@ void si_cp_dma_clear_buffer(struct radv_cmd_buffer *cmd_buffer, uint64_t va,
>         }
>  }
>
> +void si_cp_dma_wait_for_idle(struct radv_cmd_buffer *cmd_buffer)
> +{
> +       /* Issue a dummy DMA that copies zero bytes.
> +        *
> +        * The DMA engine will see that there's no work to do and skip this
> +        * DMA request, however, the CP will see the sync flag and still wait
> +        * for all DMAs to complete.
> +        */
> +       si_emit_cp_dma(cmd_buffer, 0, 0, 0, CP_DMA_SYNC);
> +}
> +
>  /* For MSAA sample positions. */
>  #define FILL_SREG(s0x, s0y, s1x, s1y, s2x, s2y, s3x, s3y)  \
>         (((s0x) & 0xf) | (((unsigned)(s0y) & 0xf) << 4) |                  \
> --
> 2.17.1
>
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