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Please follow the steps below to add the custom display timing data into the imx6qdl-seco_lvds_display.dtsi file.
Refer Verify the signal timing specifications of LCD in the datasheet and then calculate following parameters of
hback-porch, hfront-porch, vback-porch, vfront-porch, hsync-len and vsync-len
by using this open source reference , https://www.epanorama.net/faq/vga2rgb/calc.html
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hfront-porch
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vback-porch
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vfront-porch
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hsync-len
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vsync-len
LDB Structure format:
To obtain information about the structure ldb, you can refer to the documentation presents into the kernel:
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The MIPI DSI support on i.MX8 is enabled through the device trees located in the kernel source in arch/arm64/boot/dts/seco. MIPI-DSI on i.MX8 with IPU is supported with Synopsys hardware while i.MX8 uses the Mixel and the Advantec panepanels.
The SECO boards with i.MX8 SoC supports MIPI-DSI interface,
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i.MX8M boards comes with 2 display controllers: , DCSS and LCDIF.:
DCCS can be connected to HDMI, DP or MIPI-DSI and supports resolutions up to 4K.
LCDIF can be connected only to MIPI-DSI and supports resolutions up to 1080p..
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Display Interface should be added in the Linux Device Tree overlay and Panel panel must be enabled in Device tree.
The process of designing a Device Tree Overlay includes three macro steps:
writing a Device Tree Overlay (.dts) file;
generating a *.dtbo file, output of *.dts file build;
enable enabling the overlay through *.dtbo file.
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To complete panel configuration it is necessary to configure correctly the following parameters:
lvds,datamap
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: can be configured as “jeida“ or “spwg“, other configurations are not supported.
lvds,dual-channel
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: if inserted, it enables bridge dual channel output
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. The DSI video signal is splitted in LVDS channel A and LVDS channel B,
refer tosn65dsi84 datasheetfor more informations.lvds,preserve-dsi-timings
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:this parameter is usefull when LVDS display timing are synchronized with Data Enable, it should be removed if the panel is not DE sync.
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Data Enable synchronized Panel
The LVDS panel that are not synchronized with Data Enable must be configured without lvds,preserve-dsi-timing parameter and clocks = <&si5351a 0> should be commented out to ensure timing sync.
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| Note |
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All this configurations can be useless in some cases, so the panel can’t turn on. |
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recalculates the panel timing to |
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adapt them to i.MX8 DSI video output |
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a fine tuning in the admitted panel timing is necessary: clocks, front and back porch until the LVDS panel turn on. |
SECO preconfigured Panels
Below some pre-built device tree overlay files for i.MX8 boards that passed validation: 10000 cycle on/off test. Once you done the setup , you can compile the kernel with added has been defined, kernel, including LVDS display resolution, can be built. After the compilation, please copy the file into device and boot the board and by setting up the custom device tree file with support of seco_config file.
Device tree display overlay for i.MX8
Board | Module | Peripheral | Overlays |
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C12 | SMARC | MIPI-DSI to LVDS, HDMI |
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C20 | SBC | MIPI-DSI to LVDS, HDMI |
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C25 | Q7 | MIPI-DSI to LVDS, MIPI-DSI to eDP, HDMI |
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C26 | Q7 | LVDS, DP, HDMI |
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C43 | SBC | MIPI-DSI to eDP, LVDS, HDMI |
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C72 | μQ7 | MIPI-DSI to LVDS, MIPI-DSI to eDP |
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C61 | SBC | MIPI-DSI to LVDS, MIPI-DSI to eDP |
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C57 | SBC | MIPI-DSI to eDP, LVDS |
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D16 | SMARC | MIPI-DSI to eDP, LVDS, HDMI |
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