1 .. include:: <isonum.txt>
3 Qualcomm Camera Subsystem driver
4 ================================
9 This file documents the Qualcomm Camera Subsystem driver located under
10 drivers/media/platform/qcom/camss.
12 The current version of the driver supports the Camera Subsystem found on
13 Qualcomm MSM8916/APQ8016 and MSM8996/APQ8096 processors.
15 The driver implements V4L2, Media controller and V4L2 subdev interfaces.
16 Camera sensor using V4L2 subdev interface in the kernel is supported.
18 The driver is implemented using as a reference the Qualcomm Camera Subsystem
19 driver for Android as found in Code Aurora [#f1]_ [#f2]_.
22 Qualcomm Camera Subsystem hardware
23 ----------------------------------
25 The Camera Subsystem hardware found on 8x16 / 8x96 processors and supported by
26 the driver consists of:
28 - 2 / 3 CSIPHY modules. They handle the Physical layer of the CSI2 receivers.
29 A separate camera sensor can be connected to each of the CSIPHY module;
30 - 2 / 4 CSID (CSI Decoder) modules. They handle the Protocol and Application
31 layer of the CSI2 receivers. A CSID can decode data stream from any of the
32 CSIPHY. Each CSID also contains a TG (Test Generator) block which can generate
33 artificial input data for test purposes;
34 - ISPIF (ISP Interface) module. Handles the routing of the data streams from
35 the CSIDs to the inputs of the VFE;
36 - 1 / 2 VFE (Video Front End) module(s). Contain a pipeline of image processing
37 hardware blocks. The VFE has different input interfaces. The PIX (Pixel) input
38 interface feeds the input data to the image processing pipeline. The image
39 processing pipeline contains also a scale and crop module at the end. Three
40 RDI (Raw Dump Interface) input interfaces bypass the image processing
41 pipeline. The VFE also contains the AXI bus interface which writes the output
45 Supported functionality
46 -----------------------
48 The current version of the driver supports:
50 - Input from camera sensor via CSIPHY;
51 - Generation of test input data by the TG in CSID;
52 - RDI interface of VFE
54 - Raw dump of the input data to memory.
58 - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
59 V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY);
60 - MIPI RAW8 (8bit Bayer RAW - V4L2_PIX_FMT_SRGGB8 /
61 V4L2_PIX_FMT_SGRBG8 / V4L2_PIX_FMT_SGBRG8 / V4L2_PIX_FMT_SBGGR8);
62 - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P /
63 V4L2_PIX_FMT_SGBRG10P / V4L2_PIX_FMT_SGRBG10P / V4L2_PIX_FMT_SRGGB10P /
65 - MIPI RAW12 (12bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB12P /
66 V4L2_PIX_FMT_SGBRG12P / V4L2_PIX_FMT_SGRBG12P / V4L2_PIX_FMT_SRGGB12P).
67 - (8x96 only) MIPI RAW14 (14bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB14P /
68 V4L2_PIX_FMT_SGBRG14P / V4L2_PIX_FMT_SGRBG14P / V4L2_PIX_FMT_SRGGB14P).
70 - (8x96 only) Format conversion of the input data.
72 Supported input formats:
74 - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P / V4L2_PIX_FMT_Y10P).
76 Supported output formats:
78 - Plain16 RAW10 (10bit unpacked Bayer RAW - V4L2_PIX_FMT_SBGGR10 / V4L2_PIX_FMT_Y10).
80 - PIX interface of VFE
82 - Format conversion of the input data.
84 Supported input formats:
86 - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
87 V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY).
89 Supported output formats:
91 - NV12/NV21 (two plane YUV 4:2:0 - V4L2_PIX_FMT_NV12 / V4L2_PIX_FMT_NV21);
92 - NV16/NV61 (two plane YUV 4:2:2 - V4L2_PIX_FMT_NV16 / V4L2_PIX_FMT_NV61).
93 - (8x96 only) YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
94 V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY).
96 - Scaling support. Configuration of the VFE Encoder Scale module
97 for downscalling with ratio up to 16x.
99 - Cropping support. Configuration of the VFE Encoder Crop module.
101 - Concurrent and independent usage of two (8x96: three) data inputs -
102 could be camera sensors and/or TG.
105 Driver Architecture and Design
106 ------------------------------
108 The driver implements the V4L2 subdev interface. With the goal to model the
109 hardware links between the modules and to expose a clean, logical and usable
110 interface, the driver is split into V4L2 sub-devices as follows (8x16 / 8x96):
112 - 2 / 3 CSIPHY sub-devices - each CSIPHY is represented by a single sub-device;
113 - 2 / 4 CSID sub-devices - each CSID is represented by a single sub-device;
114 - 2 / 4 ISPIF sub-devices - ISPIF is represented by a number of sub-devices
115 equal to the number of CSID sub-devices;
116 - 4 / 8 VFE sub-devices - VFE is represented by a number of sub-devices equal to
117 the number of the input interfaces (3 RDI and 1 PIX for each VFE).
119 The considerations to split the driver in this particular way are as follows:
121 - representing CSIPHY and CSID modules by a separate sub-device for each module
122 allows to model the hardware links between these modules;
123 - representing VFE by a separate sub-devices for each input interface allows
124 to use the input interfaces concurently and independently as this is
125 supported by the hardware;
126 - representing ISPIF by a number of sub-devices equal to the number of CSID
127 sub-devices allows to create linear media controller pipelines when using two
128 cameras simultaneously. This avoids branches in the pipelines which otherwise
129 will require a) userspace and b) media framework (e.g. power on/off
130 operations) to make assumptions about the data flow from a sink pad to a
131 source pad on a single media entity.
133 Each VFE sub-device is linked to a separate video device node.
135 The media controller pipeline graph is as follows (with connected two / three
136 OV5645 camera sensors):
138 .. _qcom_camss_graph:
140 .. kernel-figure:: qcom_camss_graph.dot
141 :alt: qcom_camss_graph.dot
144 Media pipeline graph 8x16
146 .. kernel-figure:: qcom_camss_8x96_graph.dot
147 :alt: qcom_camss_8x96_graph.dot
150 Media pipeline graph 8x96
156 Runtime configuration of the hardware (updating settings while streaming) is
157 not required to implement the currently supported functionality. The complete
158 configuration on each hardware module is applied on STREAMON ioctl based on
159 the current active media links, formats and controls set.
161 The output size of the scaler module in the VFE is configured with the actual
162 compose selection rectangle on the sink pad of the 'msm_vfe0_pix' entity.
164 The crop output area of the crop module in the VFE is configured with the actual
165 crop selection rectangle on the source pad of the 'msm_vfe0_pix' entity.
171 APQ8016 Specification:
172 https://developer.qualcomm.com/download/sd410/snapdragon-410-processor-device-specification.pdf
173 Referenced 2016-11-24.
175 APQ8096 Specification:
176 https://developer.qualcomm.com/download/sd820e/qualcomm-snapdragon-820e-processor-apq8096sge-device-specification.pdf
177 Referenced 2018-06-22.
182 .. [#f1] https://source.codeaurora.org/quic/la/kernel/msm-3.10/
183 .. [#f2] https://source.codeaurora.org/quic/la/kernel/msm-3.18/