linux-kernel - Re: [PATCH v3 4/5] media: meson: vdec: add VP9 input support

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Message-ID: <CAMO6naw79tYi7gbwVcHyTG=T=HTNPErp352ZdFOQqzZTvz=89Q@mail.gmail.com>
Date:   Fri, 24 Jan 2020 12:18:32 +0100
From:   Maxime Jourdan <mjourdan@...libre.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 4/5] media: meson: vdec: add VP9 input support

On Thu, Jan 16, 2020 at 2:34 PM Neil Armstrong <narmstrong@...libre.com> wrote:
>
> From: Maxime Jourdan <mjourdan@...libre.com>
>
> Amlogic VP9 decoder requires an additional 16-byte payload before every
> frame header.
>
> The source buffer is updated in-place, then given to the Parser FIFO DMA.
>
> The FIFO DMA copies the blocks into the 16MiB parser ring buffer, then parses
> and copies the slice into the decoder "workspace".
>
> Signed-off-by: Maxime Jourdan <mjourdan@...libre.com>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---

[...]

> @@ -186,13 +294,27 @@ esparser_queue(struct amvdec_session *sess, struct vb2_v4l2_buffer *vbuf)
>         int ret;
>         struct vb2_buffer *vb = &vbuf->vb2_buf;
>         struct amvdec_core *core = sess->core;
> +       struct amvdec_codec_ops *codec_ops = sess->fmt_out->codec_ops;
>         u32 payload_size = vb2_get_plane_payload(vb, 0);
>         dma_addr_t phy = vb2_dma_contig_plane_dma_addr(vb, 0);
> +       u32 num_dst_bufs = 0;
>         u32 offset;
>         u32 pad_size;
>
> -       if (esparser_vififo_get_free_space(sess) < payload_size)
> +       if (sess->fmt_out->pixfmt == V4L2_PIX_FMT_VP9) {
> +               if (codec_ops->num_pending_bufs)
> +                       num_dst_bufs = codec_ops->num_pending_bufs(sess);
> +
> +               num_dst_bufs += v4l2_m2m_num_dst_bufs_ready(sess->m2m_ctx);
> +               if (sess->fmt_out->pixfmt == V4L2_PIX_FMT_VP9)
> +                       num_dst_bufs -= 2;

With the changes that happened in the updated series where one more
ref frame is held by VP9, this should be -= 3 to prevent a shortage of
CAPTURE buffers on the decoder side.

For the future, a good enhancement of the way this is handled could be
to notify new capture buffers to the decoding modules (codec_*.c), so
that they could pause when there is no capture buffer available and
resume on this notification.

> +
> +               if (esparser_vififo_get_free_space(sess) < payload_size ||
> +                   atomic_read(&sess->esparser_queued_bufs) >= num_dst_bufs)
> +                       return -EAGAIN;
> +       } else if (esparser_vififo_get_free_space(sess) < payload_size) {
>                 return -EAGAIN;
> +       }
>
>         v4l2_m2m_src_buf_remove_by_buf(sess->m2m_ctx, vbuf);
>
> @@ -206,7 +328,19 @@ esparser_queue(struct amvdec_session *sess, struct vb2_v4l2_buffer *vbuf)
>         vbuf->field = V4L2_FIELD_NONE;
>         vbuf->sequence = sess->sequence_out++;
>
> -       pad_size = esparser_pad_start_code(core, vb);
> +       if (sess->fmt_out->pixfmt == V4L2_PIX_FMT_VP9) {
> +               payload_size = vp9_update_header(core, vb);
> +
> +               /* If unable to alter buffer to add headers */
> +               if (payload_size == 0) {
> +                       amvdec_remove_ts(sess, vb->timestamp);
> +                       v4l2_m2m_buf_done(vbuf, VB2_BUF_STATE_ERROR);
> +
> +                       return 0;
> +               }
> +       }
> +
> +       pad_size = esparser_pad_start_code(core, vb, payload_size);
>         ret = esparser_write_data(core, phy, payload_size + pad_size);
>
>         if (ret <= 0) {
> --
> 2.22.0
>