157 lines
5.9 KiB
ReStructuredText
157 lines
5.9 KiB
ReStructuredText
.. include:: <isonum.txt>
|
|
|
|
Qualcomm Camera Subsystem driver
|
|
================================
|
|
|
|
Introduction
|
|
------------
|
|
|
|
This file documents the Qualcomm Camera Subsystem driver located under
|
|
drivers/media/platform/qcom/camss-8x16.
|
|
|
|
The current version of the driver supports the Camera Subsystem found on
|
|
Qualcomm MSM8916 and APQ8016 processors.
|
|
|
|
The driver implements V4L2, Media controller and V4L2 subdev interfaces.
|
|
Camera sensor using V4L2 subdev interface in the kernel is supported.
|
|
|
|
The driver is implemented using as a reference the Qualcomm Camera Subsystem
|
|
driver for Android as found in Code Aurora [#f1]_.
|
|
|
|
|
|
Qualcomm Camera Subsystem hardware
|
|
----------------------------------
|
|
|
|
The Camera Subsystem hardware found on 8x16 processors and supported by the
|
|
driver consists of:
|
|
|
|
- 2 CSIPHY modules. They handle the Physical layer of the CSI2 receivers.
|
|
A separate camera sensor can be connected to each of the CSIPHY module;
|
|
- 2 CSID (CSI Decoder) modules. They handle the Protocol and Application layer
|
|
of the CSI2 receivers. A CSID can decode data stream from any of the CSIPHY.
|
|
Each CSID also contains a TG (Test Generator) block which can generate
|
|
artificial input data for test purposes;
|
|
- ISPIF (ISP Interface) module. Handles the routing of the data streams from
|
|
the CSIDs to the inputs of the VFE;
|
|
- VFE (Video Front End) module. Contains a pipeline of image processing hardware
|
|
blocks. The VFE has different input interfaces. The PIX (Pixel) input
|
|
interface feeds the input data to the image processing pipeline. The image
|
|
processing pipeline contains also a scale and crop module at the end. Three
|
|
RDI (Raw Dump Interface) input interfaces bypass the image processing
|
|
pipeline. The VFE also contains the AXI bus interface which writes the output
|
|
data to memory.
|
|
|
|
|
|
Supported functionality
|
|
-----------------------
|
|
|
|
The current version of the driver supports:
|
|
|
|
- Input from camera sensor via CSIPHY;
|
|
- Generation of test input data by the TG in CSID;
|
|
- RDI interface of VFE - raw dump of the input data to memory.
|
|
|
|
Supported formats:
|
|
|
|
- YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
|
|
V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY);
|
|
- MIPI RAW8 (8bit Bayer RAW - V4L2_PIX_FMT_SRGGB8 /
|
|
V4L2_PIX_FMT_SGRBG8 / V4L2_PIX_FMT_SGBRG8 / V4L2_PIX_FMT_SBGGR8);
|
|
- MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P /
|
|
V4L2_PIX_FMT_SGBRG10P / V4L2_PIX_FMT_SGRBG10P / V4L2_PIX_FMT_SRGGB10P);
|
|
- MIPI RAW12 (12bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB12P /
|
|
V4L2_PIX_FMT_SGBRG12P / V4L2_PIX_FMT_SGRBG12P / V4L2_PIX_FMT_SRGGB12P).
|
|
|
|
- PIX interface of VFE
|
|
|
|
- Format conversion of the input data.
|
|
|
|
Supported input formats:
|
|
|
|
- YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
|
|
V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY).
|
|
|
|
Supported output formats:
|
|
|
|
- NV12/NV21 (two plane YUV 4:2:0 - V4L2_PIX_FMT_NV12 / V4L2_PIX_FMT_NV21);
|
|
- NV16/NV61 (two plane YUV 4:2:2 - V4L2_PIX_FMT_NV16 / V4L2_PIX_FMT_NV61).
|
|
|
|
- Scaling support. Configuration of the VFE Encoder Scale module
|
|
for downscalling with ratio up to 16x.
|
|
|
|
- Cropping support. Configuration of the VFE Encoder Crop module.
|
|
|
|
- Concurrent and independent usage of two data inputs - could be camera sensors
|
|
and/or TG.
|
|
|
|
|
|
Driver Architecture and Design
|
|
------------------------------
|
|
|
|
The driver implements the V4L2 subdev interface. 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 V4L2 sub-devices as follows:
|
|
|
|
- 2 CSIPHY sub-devices - each CSIPHY is represented by a single sub-device;
|
|
- 2 CSID sub-devices - each CSID is represented by a single sub-device;
|
|
- 2 ISPIF sub-devices - ISPIF is represented by a number of sub-devices equal
|
|
to the number of CSID sub-devices;
|
|
- 4 VFE sub-devices - VFE is represented by a number of sub-devices equal to
|
|
the number of the input interfaces (3 RDI and 1 PIX).
|
|
|
|
The considerations to split the driver in this particular way are as follows:
|
|
|
|
- representing CSIPHY and CSID modules by a separate sub-device for each module
|
|
allows to model the hardware links between these modules;
|
|
- representing VFE by a separate sub-devices for each input interface allows
|
|
to use the input interfaces concurently and independently as this is
|
|
supported by the hardware;
|
|
- representing ISPIF by a number of sub-devices equal to the number of CSID
|
|
sub-devices allows to create linear media controller pipelines when using two
|
|
cameras simultaneously. This avoids branches in the pipelines which otherwise
|
|
will require a) userspace and b) media framework (e.g. power on/off
|
|
operations) to make assumptions about the data flow from a sink pad to a
|
|
source pad on a single media entity.
|
|
|
|
Each VFE sub-device is linked to a separate video device node.
|
|
|
|
The media controller pipeline graph is as follows (with connected two OV5645
|
|
camera sensors):
|
|
|
|
.. _qcom_camss_graph:
|
|
|
|
.. kernel-figure:: qcom_camss_graph.dot
|
|
:alt: qcom_camss_graph.dot
|
|
:align: center
|
|
|
|
Media pipeline graph
|
|
|
|
|
|
Implementation
|
|
--------------
|
|
|
|
Runtime configuration of the hardware (updating settings while streaming) is
|
|
not required to implement the currently supported functionality. The complete
|
|
configuration on each hardware module is applied on STREAMON ioctl based on
|
|
the current active media links, formats and controls set.
|
|
|
|
The output size of the scaler module in the VFE is configured with the actual
|
|
compose selection rectangle on the sink pad of the 'msm_vfe0_pix' entity.
|
|
|
|
The crop output area of the crop module in the VFE is configured with the actual
|
|
crop selection rectangle on the source pad of the 'msm_vfe0_pix' entity.
|
|
|
|
|
|
Documentation
|
|
-------------
|
|
|
|
APQ8016 Specification:
|
|
https://developer.qualcomm.com/download/sd410/snapdragon-410-processor-device-specification.pdf
|
|
Referenced 2016-11-24.
|
|
|
|
|
|
References
|
|
----------
|
|
|
|
.. [#f1] https://source.codeaurora.org/quic/la/kernel/msm-3.10/
|