media: amphion: Add DMA memory tracking support

From: Ming Qian <ming.qian@oss.nxp.com>

This series adds DMA memory tracking support to the Amphion VPU driver,
allowing userspace to monitor memory consumption of codec instances.

To implement this feature in a reusable way, a new V4L2 memory tracking
infrastructure (v4l2-memtrack) is introduced, which can be adopted by
other V4L2 drivers in the future.

Background
==========

The Amphion VPU codec driver allocates various DMA buffers internally:

- Firmware boot region and RPC buffers
- Stream ring buffers
- Codec-specific buffers (MBI, DCP, reference frames)
- Encoder/decoder working buffers

These allocations are not visible to userspace, making it difficult to
debug memory issues or monitor resource usage in multi-instance scenarios
(e.g., transcoding servers with multiple simultaneous streams).

Solution
========

This series introduces:

1. V4L2_CID_MEMORY_USAGE control
   - New read-only control reporting memory usage in bytes
   - Standard V4L2 interface, queryable via VIDIOC_G_CTRL

2. v4l2-memtrack infrastructure
   - Hierarchical memory tracking (device -> instance -> queue)
   - debugfs interface at /sys/kernel/debug/v4l2-memtrack/
   - Reusable by other V4L2 drivers

3. videobuf2 integration
   - Automatic tracking of vb2 buffer allocations

4. Amphion VPU integration
   - Tracks all internal DMA allocations
   - Organized as: device -> instance -> buffers

Ming Qian (7):
  media: v4l2-ctrls: Add V4L2_CID_MEMORY_USAGE control
  docs: media: v4l2-ctrls: Add V4L2_CID_MEMORY_USAGE control
  media: v4l2-memtrack: Add V4L2 memory tracking infrastructure
  docs: media: v4l2-memtrack: Add driver API documentation
  MAINTAINERS: Add entry for V4L2 memory usage tracker
  media: videobuf2: Add memory tracking support
  media: amphion: Add V4L2 memory tracking support

 Documentation/driver-api/media/v4l2-core.rst  |   1 +
 .../driver-api/media/v4l2-memtrack.rst        | 140 +++
 .../userspace-api/media/v4l/control.rst       |  22 +-
 MAINTAINERS                                   |   8 +
 drivers/media/common/Kconfig                  |   1 +
 drivers/media/common/Makefile                 |   2 +-
 drivers/media/common/v4l2-memtrack/Kconfig    |  19 +
 drivers/media/common/v4l2-memtrack/Makefile   |   3 +
 .../common/v4l2-memtrack/v4l2-memtrack.c      | 825 ++++++++++++++++++
 .../media/common/videobuf2/videobuf2-core.c   |  13 +
 drivers/media/platform/amphion/Kconfig        |   1 +
 drivers/media/platform/amphion/vdec.c         |   9 +
 drivers/media/platform/amphion/venc.c         |   9 +
 drivers/media/platform/amphion/vpu.h          |   7 +
 drivers/media/platform/amphion/vpu_core.c     |   6 +
 drivers/media/platform/amphion/vpu_dbg.c      |   5 +
 drivers/media/platform/amphion/vpu_drv.c      |   2 +
 drivers/media/platform/amphion/vpu_v4l2.c     |  35 +-
 drivers/media/v4l2-core/v4l2-ctrls-defs.c     |   8 +
 include/media/v4l2-memtrack.h                 | 220 +++++
 include/media/videobuf2-core.h                |   4 +
 include/uapi/linux/v4l2-controls.h            |   4 +-
 22 files changed, 1340 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/driver-api/media/v4l2-memtrack.rst
 create mode 100644 drivers/media/common/v4l2-memtrack/Kconfig
 create mode 100644 drivers/media/common/v4l2-memtrack/Makefile
 create mode 100644 drivers/media/common/v4l2-memtrack/v4l2-memtrack.c
 create mode 100644 include/media/v4l2-memtrack.h


base-commit: 4fbeef21f5387234111b5d52924e77757626faa5
prerequisite-patch-id: 0000000000000000000000000000000000000000
-- 
2.53.0