media: camss: Add support for 10-bit grayscale formats
[linux-2.6-block.git] / Documentation / media / v4l-drivers / qcom_camss.rst
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1.. include:: <isonum.txt>
2
3Qualcomm Camera Subsystem driver
4================================
5
6Introduction
7------------
8
9This file documents the Qualcomm Camera Subsystem driver located under
10drivers/media/platform/qcom/camss-8x16.
11
12The current version of the driver supports the Camera Subsystem found on
13Qualcomm MSM8916 and APQ8016 processors.
14
15The driver implements V4L2, Media controller and V4L2 subdev interfaces.
16Camera sensor using V4L2 subdev interface in the kernel is supported.
17
18The driver is implemented using as a reference the Qualcomm Camera Subsystem
19driver for Android as found in Code Aurora [#f1]_.
20
21
22Qualcomm Camera Subsystem hardware
23----------------------------------
24
25The Camera Subsystem hardware found on 8x16 processors and supported by the
26driver consists of:
27
28- 2 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 CSID (CSI Decoder) modules. They handle the Protocol and Application layer
31 of the CSI2 receivers. A CSID can decode data stream from any of the CSIPHY.
32 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- VFE (Video Front End) module. Contains a pipeline of image processing hardware
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37 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
42 data to memory.
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43
44
45Supported functionality
46-----------------------
47
48The current version of the driver supports:
49
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50- Input from camera sensor via CSIPHY;
51- Generation of test input data by the TG in CSID;
52- RDI interface of VFE - raw dump of the input data to memory.
53
54 Supported formats:
55
56 - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
57 V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY);
58 - MIPI RAW8 (8bit Bayer RAW - V4L2_PIX_FMT_SRGGB8 /
59 V4L2_PIX_FMT_SGRBG8 / V4L2_PIX_FMT_SGBRG8 / V4L2_PIX_FMT_SBGGR8);
60 - MIPI RAW10 (10bit packed Bayer RAW - V4L2_PIX_FMT_SBGGR10P /
61 V4L2_PIX_FMT_SGBRG10P / V4L2_PIX_FMT_SGRBG10P / V4L2_PIX_FMT_SRGGB10P);
62 - MIPI RAW12 (12bit packed Bayer RAW - V4L2_PIX_FMT_SRGGB12P /
63 V4L2_PIX_FMT_SGBRG12P / V4L2_PIX_FMT_SGRBG12P / V4L2_PIX_FMT_SRGGB12P).
64
65- PIX interface of VFE
66
67 - Format conversion of the input data.
68
69 Supported input formats:
70
71 - YUYV/UYVY/YVYU/VYUY (packed YUV 4:2:2 - V4L2_PIX_FMT_YUYV /
72 V4L2_PIX_FMT_UYVY / V4L2_PIX_FMT_YVYU / V4L2_PIX_FMT_VYUY).
73
74 Supported output formats:
75
76 - NV12/NV21 (two plane YUV 4:2:0 - V4L2_PIX_FMT_NV12 / V4L2_PIX_FMT_NV21);
77 - NV16/NV61 (two plane YUV 4:2:2 - V4L2_PIX_FMT_NV16 / V4L2_PIX_FMT_NV61).
78
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79 - Scaling support. Configuration of the VFE Encoder Scale module
80 for downscalling with ratio up to 16x.
81
82 - Cropping support. Configuration of the VFE Encoder Crop module.
83
d226efcf 84- Concurrent and independent usage of two data inputs - could be camera sensors
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85 and/or TG.
86
87
88Driver Architecture and Design
89------------------------------
90
91The driver implements the V4L2 subdev interface. With the goal to model the
92hardware links between the modules and to expose a clean, logical and usable
93interface, the driver is split into V4L2 sub-devices as follows:
94
95- 2 CSIPHY sub-devices - each CSIPHY is represented by a single sub-device;
96- 2 CSID sub-devices - each CSID is represented by a single sub-device;
97- 2 ISPIF sub-devices - ISPIF is represented by a number of sub-devices equal
98 to the number of CSID sub-devices;
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99- 4 VFE sub-devices - VFE is represented by a number of sub-devices equal to
100 the number of the input interfaces (3 RDI and 1 PIX).
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101
102The considerations to split the driver in this particular way are as follows:
103
104- representing CSIPHY and CSID modules by a separate sub-device for each module
105 allows to model the hardware links between these modules;
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106- representing VFE by a separate sub-devices for each input interface allows
107 to use the input interfaces concurently and independently as this is
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108 supported by the hardware;
109- representing ISPIF by a number of sub-devices equal to the number of CSID
110 sub-devices allows to create linear media controller pipelines when using two
111 cameras simultaneously. This avoids branches in the pipelines which otherwise
112 will require a) userspace and b) media framework (e.g. power on/off
113 operations) to make assumptions about the data flow from a sink pad to a
114 source pad on a single media entity.
115
116Each VFE sub-device is linked to a separate video device node.
117
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118The media controller pipeline graph is as follows (with connected two OV5645
119camera sensors):
120
121.. _qcom_camss_graph:
122
123.. kernel-figure:: qcom_camss_graph.dot
124 :alt: qcom_camss_graph.dot
125 :align: center
126
127 Media pipeline graph
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128
129
130Implementation
131--------------
132
133Runtime configuration of the hardware (updating settings while streaming) is
134not required to implement the currently supported functionality. The complete
135configuration on each hardware module is applied on STREAMON ioctl based on
136the current active media links, formats and controls set.
137
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138The output size of the scaler module in the VFE is configured with the actual
139compose selection rectangle on the sink pad of the 'msm_vfe0_pix' entity.
140
141The crop output area of the crop module in the VFE is configured with the actual
142crop selection rectangle on the source pad of the 'msm_vfe0_pix' entity.
143
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144
145Documentation
146-------------
147
148APQ8016 Specification:
149https://developer.qualcomm.com/download/sd410/snapdragon-410-processor-device-specification.pdf
150Referenced 2016-11-24.
151
152
153References
154----------
155
156.. [#f1] https://source.codeaurora.org/quic/la/kernel/msm-3.10/