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In order to bring up custom display following steps are needed:

1. Kernel: Adding Custom LVDS support in Device tree file

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The target file to edit is linux-seco/arch/arm/boot/dts/imx6qdl-seco_lvds_display.dtsi. This last contains the list of available LVDS resolutions.

Code Block
cd linux-seco/arch/arm/boot/dts vi imx6qdl-seco_lvds_display.dtsi

A newest one have to be enclosed into “timing” structure.

To obtain the information about the ldb structure, you can refer to the documentation available into the Kernel:

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Below is the sample timing data for SVGA TFT LCD(800x600) 10.4 inches (BA104S01-100):

Code Block
name = LBD-SVGA-BA Clock-frequency = 39600000 Hactive = 800 Vactive = 600 Hback = 45 Hfront = 45 Vback = 25 Vfront = 25 Hsync = 10 Vsync = 10

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2. U-Boot: Adding Custom LVDS resolution into list

The resolution to use is passed from U-Boot to the kernel via bootargs. The "seco_config" command help the user to perform the selection of the video settings and resolution.
In order to add a new custom LVDS resolution:

The target file to edit is u-boot-seco/cmd/cmd_seco_config.c. This last contains the list of available LVDS resolutions to pass to kernel via bootargs (selection is performed via seco_config command).

cd linuxu-boot-seco/arch/arm/bootcmd/dts
vi imx6qdl-cmd_seco_lvds_displayconfig.dtsic

Now add the newly created ldb structure into the LVDS device tree file and save the file.Once the setup is done, you can compile the source.

U-Boot: Adding Custom LVDS resolution into list

The resolution to use is passed from U-Boot to the kernel via bootargs. The "seco_config" command help the user to perform the selection of the video settings and resolution.
In order to add a new custom LVDS resolution follow this step:

Edit file <u-boot src>/cmd/cmd_seco_config.c

This file contains the list of display setting to pass to kernel via bootargs.
The selection is performed via seco_config command.

Add the custom resolution setting with a new item into the follow structure:

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Add the custom resolution setting appending new item into the following structure:

static lvds_video_spec_t lvds_video_spec_list [] = {
        { "WVGA    [800x480]",   "LDB-WVGA",    "RGB666",      "datamap=spwg",  "",   1 },
        { "SVGA    [800x600]",   "LDB-SVGA",    "RGB666",      "datamap=spwg",  "",   1 },
        { "WVGAXGA     [800x4801024x768]",   "LDB-WVGAXGA",     "RGB666",      "datamap=spwg",  "",   1 },
        { "SVGAWXGA    [800x6001368x768]",   "LDB-SVGAWXGA",    "RGB666RGB24",       "datamap=spwgjeida",  "",   1 },
        { "XGA    WXGAP60 [1024x7681280x800]",  "LDB-XGA1280P60",     "RGB666",      "RGB24,bpp=32","datamap=spwg",  "",   1 },
        { "WXGASXGA    [1368x7681280x1024]",  "LDB-WXGASXGA",    "RGB24",       "datamap=jeida", "",   1 },
        { "WXGAP60HD1080  [1280x8001920x1080]",  "LDB-1280P601080P60", "RGB24,bpp=32",       "datamap=spwg",  "ldb=spl0", 2  1 },
        { "SXGA    [1280x1024]"<DISPLAY NAME>, <KERNEL DISPLAY NAME>, <PIXEL FORMAT>, <DATA MAPPING>, "LDB-SXGA SETTING", <CHANNEL   "RGB24",  NUMBER>}
};

with:

    RGB666     

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IPU_PIX_FMT_RGB666
    RGB565     

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 IPU_PIX_FMT_RGB565
    RGB24  

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      IPU_PIX_FMT_RGB24
  

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BGR24 

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with:

    RGB666 IPU_PIX_FMT_BGR24
    GBR24           IPU_PIX_FMT_RGB666GBR24
    RGB565YUV444          IPU_PIX_FMT_RGB565YUV444
    RGB24   YUYV        IPU_PIX_FMT_RGB24     BGR24           IPU_PIX_FMT_BGR24YUYV
    GBR24           IPU_PIX_FMT_GBR24
 UYVY   YUV444          IPU_PIX_FMT_YUV444UYVY
    YUYVYVYV            IPU_PIX_FMT_YUYVYVYU
    UYVYVYUY            IPU_PIX_FMT_UYVY
    YVYV            IPU_PIX_FMT_YVYU
    VYUY            IPU_PIX_FMT_VYUY

VYUY

Once it is done, you can boot the board using seco_config tool to configure the Device Tree Overlay.

Below are the commands for the setup:

MX6QDLS SBC-A62 U-Boot > seco_config
 __________________________________________________
                     Chose Video Setting.
 __________________________________________________
1) no display
2) LVDS
3) HDMI
4) LVDS - LVDS (clone)
5) LVDS - LVDS (dual)
6) LVDS - HDMI
7) HDMI - LVDS
> 2

 __________________________________________________
        Chose LVDS resolution for LVDS1.
 __________________________________________________
1) WVGA	   [800x480]
2) SVGA	   [800x600]
3) XGA	   [1024x768]
4) WXGA	   [1368x768]
5) WXGAP60 [1280x800]
6) SXGA	   [1280x1024]
7) HD1080  [1920x1080]
> 1

 __________________________________________________
     Chose FDT overlay option for touch screen controller.
 __________________________________________________
1) not use
2) st1232
3) gt928
> 2

 __________________________________________________
     Chose FDT overlay option for J8 Expansion Connector configurator.
 __________________________________________________
1) defalut
2) custom
> 1


Saving Environment to MMC... Writing to MMC(1)... OK
X6QDLS SBC-A62 U-Boot > saveenv  
Saving Environment to MMC... Writing to MMC(1)... OK
MX6QDLS SBC-A62 U-Boot > printenv fdt_file      
fdt_file=imx6q-seco_SBC_A62.dtb
MX6QDLS SBC-A62 U-Boot > printenv fdt_overlay_video_list 
fdt_overlay_video_list=imx6qdl-seco_SBC_A62_video_LVDS.dtbo
MX6QDLS SBC-A62 U-Boot > printenv fdt_overlay_per_list   
fdt_overlay_per_list=imx6qdl-seco_SBC_A62_touch_st1232.dtbo 
MX6QDLS SBC-A62 U-Boot > boot
SECO i.MX Distro with XWayload backend 4.19-warrior secoboards ttymxc1

secoboards login: root
password:
ast login: Thu Sep 16 06:50:45 UTC 2021 on tty7
root@secoboards:~# 

U-Boot: Adding Custom LVDS resolution for Splash Screen

Also the U-Boot uses the Display to display the Splash Screen. So, if the scope is to use also the custom resolution also at U-Boot level, this task have to be performed:

Editing the file board/seco/common/display.c

A new node into “struct display_info_t const displays[]” must to be added. Under the sub-structure

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3. U-Boot: Adding Custom LVDS resolution for Splash Screen

Also the U-Boot uses the Display to display the Splash Screen. So, if the scope is to use also the custom resolution at U-Boot level, this task have to be performed:

Editing the file board/seco/common/display.c

A new node into “struct display_info_t const displays[]” must to be added. Under the sub-structure

}, {
                .bus    = -1,
                .addr   = -1,
                .pixfmt = IPU_PIX_FMT_RGB24,
                .detect = NULL,
                .enable = enable_lvds,
                .mode   = {
                        // Rif. Panel 1024x768 Panel UMSH-8596MD-15T
                        .name           = "LDB-1280P60",
                        .refresh        = 60,
                        .xres           = 1280,
                        .busyres           = -1800,
                        .pixclock    .addr   = -115128,
                .pixfmt = IPU_PIX_FMT_RGB24,      .left_margin    = 220,
     .detect = NULL,                 .enableright_margin   = enable_lvds40,
                 .mode    = {  .upper_margin   = 21,
                  // Rif. Panel 1024x768 Panel UMSH-8596MD-15T
 .lower_margin   = 7,
                   .name     .hsync_len      = "LDB-1280P60"60,
                        .refresh  .vsync_len      = 6010,
                        .xressync           = 12800,
                        .yresvmode          = = 800,FB_VMODE_NONINTERLACED
                }
        .pixclock       = 15128,
                        .left_margin    = 220,
                        .right_margin   = 40,
                        .upper_margin   = 21,
                        .lower_margin   = 7,
                        .hsync_len      = 60,},

Insert the new custom resolution, starting from the one above and edit the sub-structure "mode", considering the following fields:

4. Boot with new resolution

• Set right resolution at U-Boot:

setenv panel "<resolution name>
saveen

• Set right resolution at kernel, using seco_config command:

MX6QDLS SBC-A62 U-Boot > seco_config

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 __________________________________________________
                     Chose Video  Setting.vsync_len      = 10,
                        .sync           = 0,
        
 __________________________________________________
1) no display
2) LVDS
3) HDMI
4) LVDS - LVDS (clone)
5) LVDS - LVDS (dual)
6) LVDS - HDMI
7) HDMI - LVDS
> 2

 __________________________________________________
        Chose LVDS resolution for    LVDS1.vmode          = FB_VMODE_NONINTERLACED
                }
        },

Insert the new custom resolution, starting from the one above and edit the sub-structure "mode", considering the following fields:

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Field

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Description

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name

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name of the resolution, to use at U-Boot level

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refresh

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refrash rate of the panel (pixecl clock / [ ( tot horiz. pixel) * (tot vert. pixel) ]

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xres

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horizontal active area

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yres

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vertical active area

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pixclock

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pixel clock in pico seconds

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left_margin

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horizontal back porch

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right_margin

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horizontal fromt porch

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upper_margin

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vertical back porch

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lower_margin

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vertical fromt porch

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hsync_len

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horizontal SYNC

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vsync_len

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vertical SYNC

To select the right display resolution at run time, set the "panel" variable according to the associated name into structure above:

setenv panel "<resolution name>
saveen
 __________________________________________________
1) WVGA	   [800x480]
2) SVGA	   [800x600]
3) XGA	   [1024x768]
4) WXGA	   [1368x768]
5) WXGAP60 [1280x800]
6) SXGA	   [1280x1024]
7) HD1080  [1920x1080]
8) NEW_RESOLUTION
> 8

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Saving Environment to MMC... Writing to MMC(1)... OK

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Display Customization Guide for i.MX8

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