[PATCH v8.1 10/10] media: Documentation: Add documentation file c3-isp.rst

From: Jacopo Mondi
Date: Tue Apr 15 2025 - 11:04:07 EST

From: Keke Li <keke.li@xxxxxxxxxxx>

Add the file 'c3-isp.rst' that documents the c3-isp driver.

Signed-off-by: Keke Li <keke.li@xxxxxxxxxxx>
Signed-off-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/media/c3-isp.dot | 26 +++++
Documentation/admin-guide/media/c3-isp.rst | 101 ++++++++++++++++++
.../admin-guide/media/v4l-drivers.rst | 1 +
MAINTAINERS | 2 +
4 files changed, 130 insertions(+)
create mode 100644 Documentation/admin-guide/media/c3-isp.dot
create mode 100644 Documentation/admin-guide/media/c3-isp.rst

diff --git a/Documentation/admin-guide/media/c3-isp.dot b/Documentation/admin-guide/media/c3-isp.dot
new file mode 100644
index 000000000000..42dc931ee84a
--- /dev/null
+++ b/Documentation/admin-guide/media/c3-isp.dot
@@ -0,0 +1,26 @@
+digraph board {
+ rankdir=TB
+ n00000001 [label="{{<port0> 0 | <port1> 1} | c3-isp-core\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3 | <port4> 4 | <port5> 5}}", shape=Mrecord, style=filled, fillcolor=green]
+ n00000001:port3 -> n00000008:port0
+ n00000001:port4 -> n0000000b:port0
+ n00000001:port5 -> n0000000e:port0
+ n00000001:port2 -> n00000027
+ n00000008 [label="{{<port0> 0} | c3-isp-resizer0\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+ n00000008:port1 -> n00000016 [style=bold]
+ n0000000b [label="{{<port0> 0} | c3-isp-resizer1\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+ n0000000b:port1 -> n0000001a [style=bold]
+ n0000000e [label="{{<port0> 0} | c3-isp-resizer2\n/dev/v4l-subdev3 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+ n0000000e:port1 -> n00000023 [style=bold]
+ n00000011 [label="{{<port0> 0} | c3-mipi-adapter\n/dev/v4l-subdev4 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+ n00000011:port1 -> n00000001:port0 [style=bold]
+ n00000016 [label="c3-isp-cap0\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
+ n0000001a [label="c3-isp-cap1\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
+ n0000001e [label="{{<port0> 0} | c3-mipi-csi2\n/dev/v4l-subdev5 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+ n0000001e:port1 -> n00000011:port0 [style=bold]
+ n00000023 [label="c3-isp-cap2\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
+ n00000027 [label="c3-isp-stats\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
+ n0000002b [label="c3-isp-params\n/dev/video4", shape=box, style=filled, fillcolor=yellow]
+ n0000002b -> n00000001:port1
+ n0000003f [label="{{} | imx290 2-001a\n/dev/v4l-subdev6 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
+ n0000003f:port0 -> n0000001e:port0 [style=bold]
+}
diff --git a/Documentation/admin-guide/media/c3-isp.rst b/Documentation/admin-guide/media/c3-isp.rst
new file mode 100644
index 000000000000..bc5e2f836e8d
--- /dev/null
+++ b/Documentation/admin-guide/media/c3-isp.rst
@@ -0,0 +1,101 @@
+.. SPDX-License-Identifier: (GPL-2.0-only OR MIT)
+
+.. include:: <isonum.txt>
+
+=================================================
+Amlogic C3 Image Signal Processing (C3ISP) driver
+=================================================
+
+Introduction
+============
+
+This file documents the Amlogic C3ISP driver located under
+drivers/media/platform/amlogic/c3/isp.
+
+The current version of the driver supports the C3ISP found on
+Amlogic C308L processor.
+
+The driver implements V4L2, Media controller and V4L2 subdev interfaces.
+Camera sensor using V4L2 subdev interface in the kernel is supported.
+
+The driver has been tested on AW419-C308L-Socket platform.
+
+Amlogic C3 ISP
+==============
+
+The Camera hardware found on C308L processors and supported by
+the driver consists of:
+
+- 1 MIPI-CSI-2 module: handles the physical layer of the MIPI CSI-2 receiver and
+ receive data from the connected camera sensor.
+- 1 MIPI-ADAPTER module: organize MIPI data to meet ISP input requirements and
+ send MIPI data to ISP.
+- 1 ISP (Image Signal Processing) module: contain a pipeline of image processing
+ hardware blocks. The ISP pipeline contains three resizers at the end each of
+ them connected to a DMA interface which writes the output data to memory.
+
+An high level functional view of the C3 ISP is presented below.::
+
+ +----------+ +-------+
+ | Resizer |--->| WRMIF |
+ +---------+ +------------+ +--------------+ +-------+ |----------+ +-------+
+ | Sensor |--->| MIPI CSI-2 |--->| MIPI ADAPTER |--->| ISP |---|----------+ +-------+
+ +---------+ +------------+ +--------------+ +-------+ | Resizer |--->| WRMIF |
+ +----------+ +-------+
+ |----------+ +-------+
+ | Resizer |--->| WRMIF |
+ +----------+ +-------+
+
+Driver architecture and design
+==============================
+
+With the goal to model the hardware links between the modules and to expose a
+clean, logical and usable interface, the driver is split into the
+following V4L2 sub-devices:
+
+- 1 `c3-mipi-csi2` sub-device - the MIPI CSI-2 receiver
+- 1 `c3-mipi-adapter` sub-device - the MIPI adapter
+- 1 `c3-isp-core` sub-device - the ISP core
+- 3 `c3-isp-resizer` sub-devices - the ISP resizers
+
+The `c3-isp-core` sub-device is linked to 2 video device nodes for statistics
+capture and parameters programming:
+
+- the `c3-isp-stats` capture video device node for statistics capture
+- the `c3-isp-params` output video device for parameters programming
+
+Each `c3-isp-resizer` sub-device is linked to a capture video device node where
+frames are captured from:
+
+- `c3-isp-resizer0` is linked to the `c3-isp-cap0` capture video device
+- `c3-isp-resizer1` is linked to the `c3-isp-cap1` capture video device
+- `c3-isp-resizer2` is linked to the `c3-isp-cap2` capture video device
+
+The media controller pipeline graph is as follows (with connected a
+IMX290 camera sensor):
+
+.. _isp_topology_graph:
+
+.. kernel-figure:: c3-isp.dot
+ :alt: c3-isp.dot
+ :align: center
+
+ Media pipeline topology
+
+Implementation
+==============
+
+Runtime configuration of the ISP hardware is performed on the `c3-isp-params`
+video device node using the :ref:`V4L2_META_FMT_C3ISP_PARAMS
+<v4l2-meta-fmt-c3isp-params>` as data format. The buffer structure is defined by
+:c:type:`c3_isp_params_cfg`.
+
+Statistics are captured from the `c3-isp-stats` video device node using the
+:ref:`V4L2_META_FMT_C3ISP_STATS <v4l2-meta-fmt-c3isp-stats>` data format.
+
+The final picture size and format is configured using the V4L2 video
+capture interface on the `c3-isp-cap[0, 2]` video device nodes.
+
+The Amlogic C3 ISP is supported by `libcamera <https://libcamera.org>`_ with a
+dedicated pipeline handler and algorithms that perform run-time image correction
+and enhancement.
diff --git a/Documentation/admin-guide/media/v4l-drivers.rst b/Documentation/admin-guide/media/v4l-drivers.rst
index e8761561b2fe..3bac5165b134 100644
--- a/Documentation/admin-guide/media/v4l-drivers.rst
+++ b/Documentation/admin-guide/media/v4l-drivers.rst
@@ -10,6 +10,7 @@ Video4Linux (V4L) driver-specific documentation
:maxdepth: 2

bttv
+ c3-isp
cafe_ccic
cx88
fimc
diff --git a/MAINTAINERS b/MAINTAINERS
index d165b806aa8f..0b83cc99b429 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1257,6 +1257,8 @@ AMLOGIC ISP DRIVER
M: Keke Li <keke.li@xxxxxxxxxxx>
L: linux-media@xxxxxxxxxxxxxxx
S: Maintained
+F: Documentation/admin-guide/media/c3-isp.dot
+F: Documentation/admin-guide/media/c3-isp.rst
F: Documentation/devicetree/bindings/media/amlogic,c3-isp.yaml
F: Documentation/userspace-api/media/v4l/metafmt-c3-isp.rst
F: drivers/media/platform/amlogic/c3/isp/
--
2.48.1