66 lines
2.9 KiB
ReStructuredText
66 lines
2.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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The VPBE V4L2 driver design
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===========================
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Functional partitioning
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-----------------------
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Consists of the following:
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1. V4L2 display driver
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Implements creation of video2 and video3 device nodes and
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provides v4l2 device interface to manage VID0 and VID1 layers.
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2. Display controller
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Loads up VENC, OSD and external encoders such as ths8200. It provides
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a set of API calls to V4L2 drivers to set the output/standards
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in the VENC or external sub devices. It also provides
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a device object to access the services from OSD subdevice
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using sub device ops. The connection of external encoders to VENC LCD
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controller port is done at init time based on default output and standard
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selection or at run time when application change the output through
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V4L2 IOCTLs.
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When connected to an external encoder, vpbe controller is also responsible
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for setting up the interface between VENC and external encoders based on
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board specific settings (specified in board-xxx-evm.c). This allows
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interfacing external encoders such as ths8200. The setup_if_config()
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is implemented for this as well as configure_venc() (part of the next patch)
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API to set timings in VENC for a specific display resolution. As of this
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patch series, the interconnection and enabling and setting of the external
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encoders is not present, and would be a part of the next patch series.
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3. VENC subdevice module
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Responsible for setting outputs provided through internal DACs and also
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setting timings at LCD controller port when external encoders are connected
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at the port or LCD panel timings required. When external encoder/LCD panel
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is connected, the timings for a specific standard/preset is retrieved from
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the board specific table and the values are used to set the timings in
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venc using non-standard timing mode.
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Support LCD Panel displays using the VENC. For example to support a Logic
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PD display, it requires setting up the LCD controller port with a set of
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timings for the resolution supported and setting the dot clock. So we could
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add the available outputs as a board specific entry (i.e add the "LogicPD"
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output name to board-xxx-evm.c). A table of timings for various LCDs
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supported can be maintained in the board specific setup file to support
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various LCD displays.As of this patch a basic driver is present, and this
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support for external encoders and displays forms a part of the next
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patch series.
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4. OSD module
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OSD module implements all OSD layer management and hardware specific
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features. The VPBE module interacts with the OSD for enabling and
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disabling appropriate features of the OSD.
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Current status
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--------------
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A fully functional working version of the V4L2 driver is available. This
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driver has been tested with NTSC and PAL standards and buffer streaming.
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