1.. SPDX-License-Identifier: GPL-2.0
2
3.. include:: <isonum.txt>
4
5Qualcomm Camera Subsystem driver
6================================
7
8Introduction
9------------
10
11This file documents the Qualcomm Camera Subsystem driver located under
12drivers/media/platform/qcom/camss.
13
14The current version of the driver supports the Camera Subsystem found on
15Qualcomm MSM8916/APQ8016 and MSM8996/APQ8096 processors.
16
17The driver implements V4L2, Media controller and V4L2 subdev interfaces.
18Camera sensor using V4L2 subdev interface in the kernel is supported.
19
20The driver is implemented using as a reference the Qualcomm Camera Subsystem
21driver for Android as found in Code Linaro [#f1]_ [#f2]_.
22
23
24Qualcomm Camera Subsystem hardware
25----------------------------------
26
27The Camera Subsystem hardware found on 8x16 / 8x96 processors and supported by
28the driver consists of:
29
30- 2 / 3 CSIPHY modules. They handle the Physical layer of the CSI2 receivers.
31  A separate camera sensor can be connected to each of the CSIPHY module;
32- 2 / 4 CSID (CSI Decoder) modules. They handle the Protocol and Application
33  layer of the CSI2 receivers. A CSID can decode data stream from any of the
34  CSIPHY. Each CSID also contains a TG (Test Generator) block which can generate
35  artificial input data for test purposes;
36- ISPIF (ISP Interface) module. Handles the routing of the data streams from
37  the CSIDs to the inputs of the VFE;
38- 1 / 2 VFE (Video Front End) module(s). Contain a pipeline of image processing
39  hardware blocks. The VFE has different input interfaces. The PIX (Pixel) input
40  interface feeds the input data to the image processing pipeline. The image
41  processing pipeline contains also a scale and crop module at the end. Three
42  RDI (Raw Dump Interface) input interfaces bypass the image processing
43  pipeline. The VFE also contains the AXI bus interface which writes the output
44  data to memory.
45
46
47Supported functionality
48-----------------------
49
50The current version of the driver supports:
51
52- Input from camera sensor via CSIPHY;
53- Generation of test input data by the TG in CSID;
54- RDI interface of VFE
55
56  - Raw dump of the input data to memory.
57
58    Supported formats:
59
60    - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
61      V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY);
62    - MIPI RAW8 (8bit Bayer RAW - V4L2_PIX_FMT_SRGGB8 /
63      V4L2_PIX_FMT_SGRBG8 / V4L2_PIX_FMT_SGBRG8 / V4L2_PIX_FMT_SBGGR8);
64    - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P /
65      V4L2_PIX_FMT_SGBRG10P / V4L2_PIX_FMT_SGRBG10P / V4L2_PIX_FMT_SRGGB10P /
66      V4L2_PIX_FMT_Y10P);
67    - MIPI RAW12 (12bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB12P /
68      V4L2_PIX_FMT_SGBRG12P / V4L2_PIX_FMT_SGRBG12P / V4L2_PIX_FMT_SRGGB12P).
69    - (8x96 only) MIPI RAW14 (14bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB14P /
70      V4L2_PIX_FMT_SGBRG14P / V4L2_PIX_FMT_SGRBG14P / V4L2_PIX_FMT_SRGGB14P).
71
72  - (8x96 only) Format conversion of the input data.
73
74    Supported input formats:
75
76    - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P / V4L2_PIX_FMT_Y10P).
77
78    Supported output formats:
79
80    - Plain16 RAW10 (10bit unpacked Bayer RAW - V4L2_PIX_FMT_SBGGR10 / V4L2_PIX_FMT_Y10).
81
82- PIX interface of VFE
83
84  - Format conversion of the input data.
85
86    Supported input formats:
87
88    - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
89      V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY).
90
91    Supported output formats:
92
93    - NV12/NV21 (two plane YUV 4:2:0 - V4L2_PIX_FMT_NV12 / V4L2_PIX_FMT_NV21);
94    - NV16/NV61 (two plane YUV 4:2:2 - V4L2_PIX_FMT_NV16 / V4L2_PIX_FMT_NV61).
95    - (8x96 only) YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
96      V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY).
97
98  - Scaling support. Configuration of the VFE Encoder Scale module
99    for downscalling with ratio up to 16x.
100
101  - Cropping support. Configuration of the VFE Encoder Crop module.
102
103- Concurrent and independent usage of two (8x96: three) data inputs -
104  could be camera sensors and/or TG.
105
106
107Driver Architecture and Design
108------------------------------
109
110The driver implements the V4L2 subdev interface. With the goal to model the
111hardware links between the modules and to expose a clean, logical and usable
112interface, the driver is split into V4L2 sub-devices as follows (8x16 / 8x96):
113
114- 2 / 3 CSIPHY sub-devices - each CSIPHY is represented by a single sub-device;
115- 2 / 4 CSID sub-devices - each CSID is represented by a single sub-device;
116- 2 / 4 ISPIF sub-devices - ISPIF is represented by a number of sub-devices
117  equal to the number of CSID sub-devices;
118- 4 / 8 VFE sub-devices - VFE is represented by a number of sub-devices equal to
119  the number of the input interfaces (3 RDI and 1 PIX for each VFE).
120
121The considerations to split the driver in this particular way are as follows:
122
123- representing CSIPHY and CSID modules by a separate sub-device for each module
124  allows to model the hardware links between these modules;
125- representing VFE by a separate sub-devices for each input interface allows
126  to use the input interfaces concurrently and independently as this is
127  supported by the hardware;
128- representing ISPIF by a number of sub-devices equal to the number of CSID
129  sub-devices allows to create linear media controller pipelines when using two
130  cameras simultaneously. This avoids branches in the pipelines which otherwise
131  will require a) userspace and b) media framework (e.g. power on/off
132  operations) to  make assumptions about the data flow from a sink pad to a
133  source pad on a single media entity.
134
135Each VFE sub-device is linked to a separate video device node.
136
137The media controller pipeline graph is as follows (with connected two / three
138OV5645 camera sensors):
139
140.. _qcom_camss_graph:
141
142.. kernel-figure:: qcom_camss_graph.dot
143    :alt:   qcom_camss_graph.dot
144    :align: center
145
146    Media pipeline graph 8x16
147
148.. kernel-figure:: qcom_camss_8x96_graph.dot
149    :alt:   qcom_camss_8x96_graph.dot
150    :align: center
151
152    Media pipeline graph 8x96
153
154
155Implementation
156--------------
157
158Runtime configuration of the hardware (updating settings while streaming) is
159not required to implement the currently supported functionality. The complete
160configuration on each hardware module is applied on STREAMON ioctl based on
161the current active media links, formats and controls set.
162
163The output size of the scaler module in the VFE is configured with the actual
164compose selection rectangle on the sink pad of the 'msm_vfe0_pix' entity.
165
166The crop output area of the crop module in the VFE is configured with the actual
167crop selection rectangle on the source pad of the 'msm_vfe0_pix' entity.
168
169
170Documentation
171-------------
172
173APQ8016 Specification:
174https://developer.qualcomm.com/download/sd410/snapdragon-410-processor-device-specification.pdf
175Referenced 2016-11-24.
176
177APQ8096 Specification:
178https://developer.qualcomm.com/download/sd820e/qualcomm-snapdragon-820e-processor-apq8096sge-device-specification.pdf
179Referenced 2018-06-22.
180
181References
182----------
183
184.. [#f1] https://git.codelinaro.org/clo/la/kernel/msm-3.10/
185.. [#f2] https://git.codelinaro.org/clo/la/kernel/msm-3.18/
186