On 09/11/2018 05:09 PM, Maxime Jourdan wrote:

Hi everyone,

This patch series adds support for the Amlogic video decoder,
as well as the corresponding dt bindings for GXBB/GXL/GXM chips.

It features decoding for the following formats:
- MPEG 1
- MPEG 2

The following formats will be added in future patches:
- MJPEG
- MPEG 4 (incl. Xvid, H.263)
- H.264
- HEVC (incl. 10-bit)

The following formats' development has still not started, but they are
supported by the hardware:
- VC1
- VP9

The code was made in such a way to allow easy inclusion of those formats
in the future.

The decoder is single instance.

Files:
 - vdec.c handles the V4L2 M2M logic
 - esparser.c manages the hardware bitstream parser
 - vdec_helpers.c provides helpers to DONE the dst buffers as well as
 various common code used by the codecs
 - vdec_1.c manages the VDEC_1 block of the vdec IP
 - codec_mpeg12.c enables decoding for MPEG 1/2.
 - vdec_platform.c links codec units with vdec units
 (e.g vdec_1 with codec_mpeg12) and lists all the available
 src/dst formats and requirements (max width/height, etc.),
 per compatible chip.

Firmwares are necessary to run the vdec. They can currently be found at:
https://github.com/chewitt/meson-firmware

It was tested primarily with ffmpeg's v4l2-m2m implementation. For instance:
$ ffmpeg -c:v mpeg2_v4l2m2m -i sample_mpeg2.mkv -f null -

Note: This patch series depends on
"[PATCH v3 0/3] soc: amlogic: add meson-canvas"
https://patchwork.kernel.org/cover/10573763/

The v4l2-compliance results are available below the patch diff.

Changes since v1 [0]:
 - use named interrupts in the bindings
 - rewrite description in the bindings doc
 - don't include the dts changes in the patch series
 - fill the vb2 queues locks
 - fill the video_device lock
 - use helpers for wait_prepare and wait_finish vb2_ops
 - remove unnecessary usleep in between esparser writes.
 Extensive testing of every codec on GXBB/GXL didn't reveal
 any fails without it, so just remove it.
 - compile v4l2_compliance inside the git repo
 - Check for plane number/plane size to pass the latest v4l2-compliance test
 - Moved the single instance check (returning -EBUSY) to start/stop streaming
 The check was previously in queue_setup but there was no great location to
 clear it except for .close().

Actually, you can clear it by called VIDIOC_REQBUFS with count set to 0. That
freed all buffers and clears this.

Now, the difference between queue_setup and start/stop streaming is that if you
do this in queue_setup you'll know early on that the device is busy. It is
reasonable to assume that you only allocate buffers when you also want to start
streaming, so that it a good place to know this quickly.

Whereas with start_streaming you won't know until you call STREAMON, or even later
if you start streaming with no buffers queued, since start_streaming won't
be called until you have at least 'min_buffers_needed' buffers queued (1 for this
driver). So in that case EBUSY won't be returned until the first VIDIOC_QBUF.

My preference is to check this in queue_setup, but it is up to you to decide.
Just be aware of the difference between the two options.

Regards,

	Hans