Page Comparison

Introduction

Aim The aim of this section is to properly configure LVDS settings.

LVDS Display Bridge (LDB) is used to connect the IPU (Image Processing Unit) to the External LVDS Display Interface. Its purpose is to support flow of synchronous RGB data from the IPU to external display devices through the LVDS interface.

Device Tree Overlay

Device Tree Overlays (DTO) provide a way to modify the overall device tree without re-compiling the complete device tree.
Overlays are fragments of a complete device tree that can be included or removed according with the environment. Direct consequence is enabling/disabling hardware components in the system.

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 the overlay through *.dtbo file.

For further information about overlay device tree customization, you can refer to the documentation available at following Kernel path:

linux-seco/Documentation/devicetree/overlay-notes.txt

Some devices are used in overlays and those devices are pre-enabled by default in the source, Below the reference table for pre-enabled device tree overlay.

Eg: display, touch, cpld, gpio available in overlay.

...

Boards family

...

Peripherals

...

Device tree overlay

...

i.MX6

...

UART, LVDS, RGB, Audio, HDMI, Touch, GPIO, Pin header selection…

You can find the pre-enabled device tree overlay

...

imx6qdl-seco_i.MX6XXX_uart4.dtbo ,imx6qdl-seco_i.MX6XXX_video_LVDS.dtbo,imx6qdl-seco_i.MX6XXX_ac97.dtbo,imx6qdl-seco_i.MX6XXX_video_HDMI.dtbo,imx6qdl-seco_i.MX6XXX_cpld_gpio_pwm.dtbo,imx6qdl-seco_i.MX6XXX_touch_st1232.dtbo,imx6sx-seco_i.MX6XXX_conn_j9.dtbo,imx6sx-seco_i.MX6XXX_RGB.dtbo

...

i.MX8

...

HDMI, Display Port, LVDS , Camera, hdmiin, lcdif, Modem, eDP, GPIO,CAN, RTC,PCIe, SPI, DCSS, WiFi/BT …

You can find the pre-enabled device tree overlay

...

seco-i.MX8XXX-hdmi.dtbo,seco-i.MX8XXX-dp.dtbo,seco-i.MX8XXX-lvds-dual.dtbo,seco-i.MX8XXX-ov5640-csi0.dtbo,seco-i.MX8XXX-hdmiin.dtbo,seco-i.MX8XXX-lcdif-sn65dsi86.dtbo,seco-i.MX8XXX-modem.dtbo,seco-i.MX8XXX-port1-can.dtbo,seco-i.MX8XXX-port1-rs232.dtbo,seco-i.MX8XXX-wilink.dtbo

LVDS Customization Guide for i.MX6

The i.MX6 based modules use the fbdev interface for mode setting and output configuration.
Two IPU units are on the imx6q SOC while only one IPU unit on the imx6dl SOC. Each IPU unit has two display interfaces. The Vivante X driver can only make use of the first framebuffer /dev/fb0 while the others can be used through the fbdev framebuffer interface.

The assignment of the possible display outputs to the framebuffers (scan-out engines) and their timing configuration can be done both through Kernel command line and within the device tree. The command line settings take precedence over the device tree.
The first and third video output has an additional overlay framebuffer configured.

...

Video output

...

IPU core

...

fb boot name

...

fb device

...

overlay fb device

...

First

...

IPU1

...

mxcfb0

...

/dev/fb0

...

/dev/fb1

...

Second

...

IPU1

...

mxcfb1

...

/dev/fb2

...

Third

...

IPU2

...

mxcfb2

...

/dev/fb3

...

/dev/fb4

...

Fourth

...

IPU2

...

mxcfb3

...

/dev/fb5

Adding Custom LVDS support in Device tree file for i.MX6

Please follow the steps below to add the custom display timing data into the imx6qdl-seco_lvds_display.dtsi file.

Refer the signal timing specifications of LCD in the datasheet & then calculate the parameters of using this open source reference, https://www.epanorama.net/faq/vga2rgb/calc.html

1. hback-porch

2. hfront-porch

3. vback-porch

4. vfront-porch

5. hsync-len

6. vsync-len

LDB Structure format:

To obtain information about the structure ldb, you can refer to the documentation presents into the kernel:

linux-seco/Documentation/devicetree/bindings/display/imx/ldb.txt
linux-seco/Documentation/devicetree/bindings/fb/fsl_ipuv3_fb.txt

        timing9: $name { 
		      clock-frequency = <$Clock-frequency>; 
			  hactive = <$Hactive>; 
			  vactive = <$Vactive>; 
			  hback-porch = <$Hback>; 
			  hfront-porch = <$Hfront>; 
			  vback-porch = <$Vback>; 
			  vfront-porch = <$Vfront>; 
			  hsync-len = <$Hsync>; 
			  vsync-len = <$Vsync>; 
		};

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

...

custom display: LVDS and eDP panels.

...

Standard Display Timings

Verify the signal timing specifications of the LCD in the datasheet and then calculate following parameters:

...

...

LVDS Customization Guide for i.MX6

In order to bring up a custom display, follow the steps below.

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

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

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

In order to add a new LVDS into the above mentioned list, timing structure must be modified to include it.

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

• linux-seco/Documentation/devicetree/bindings/display/imx/ldb.txt

• linux-seco/Documentation/devicetree/bindings/fb/fsl_ipuv3_fb.txt

Below is the data timing structure:

        timing9: $name { 
		      clock-frequency = <$Clock-frequency>; 
			  hactive = <$Hactive>; 
			  vactive = <$Vactive>; 
			  hback-porch = <$Hback>; 
			  hfront-porch = <$Hfront>; 
			  vback-porch = <$Vback>; 
			  vfront-porch = <$Vfront>; 
			  hsync-len = <$Hsync>; 
			  vsync-len = <$Vsync>; 
		};

Below is an example of ldb structure got for SVGA TFT LCD(800x600 BA104S01-100 ) 10.4 inches panel (datasheet avalaible here).

...

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

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, please follow the steps described below:

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

cd u-boot-seco/cmd/
vi cmd_seco_config.c

• Add the custom resolution settings by appending new items 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 },
        { "XGA     [1024x768]",  "LDB-XGA",     "RGB666",      "datamap=spwg",  "",   1 },
        { "WXGA    [1368x768]", name = LBD-SVGA-BA"LDB-WXGA",    "RGB24",         "datamap=jeida", "",   1 },
    Clock-frequency = 39600000  { "WXGAP60 [1280x800]",  "LDB-1280P60", "RGB24,bpp=32","datamap=spwg",  "",   1 },
        Hactive{ ="SXGA 800   [1280x1024]", "LDB-SXGA",    "RGB24",       "datamap=jeida", "",   1 },
 Vactive = 600     { "HD1080      [1920x1080]", "LDB-1080P60", "RGB24",          Hback = 45
                     Hfront = 45
"datamap=spwg", "ldb=spl0", 2 },
        {<DISPLAY NAME>, <KERNEL DISPLAY NAME>, <PIXEL FORMAT>, <DATA MAPPING>, "LDB SETTING", <CHANNEL Vback = 25 
                     Vfront = 25 
             NUMBER>}
};

The fields <DISPLAY NAME>, <KERNEL DISPLAY NAME>, <PIXEL FORMAT>, <DATA MAPPING>, "LDB SETTING", <CHANNEL NUMBER> are described in the table below:

    RGB666          

...

IPU_PIX_FMT_RGB666
    RGB565          IPU_PIX_FMT_RGB565
    RGB24    

...

...

Then getting into device tree path (arch/arm/boot/dts/imx6qdl-seco_lvds_display.dtsi),Please find below ldb structure to be add in the imx6qdl-seco_lvds_display.dtsi file.

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

Add the created new LDB structure into LVDS device tree file and save the file.

Now you can check the device tree overlay file whether LVDS (ldb) enabled or not. Below the example to enable the ldb node.

...

      IPU_PIX_FMT_RGB24
    BGR24           IPU_PIX_FMT_BGR24
    GBR24           IPU_PIX_

...

FMT_

...

GBR24

...

    YUV444          

...

IPU_PIX_FMT_YUV444
    YUYV 

...

Once you are done the setup,you can compile the source.

Device tree display overlay for i.MX6

...

Board

...

Module

...

Peripheral

...

Overlays

...

928

...

Q7

HDMI,

LVDS

...

imx6qdl-seco_quadmo747_928_video_LVDS.dtbo
imx6qdl-seco_quadmo747_928_video_LVDSx2_CLONE.dtbo
imx6qdl-seco_quadmo747_928_video_LVDSx2_DUAL.dtbo
imx6qdl-seco_quadmo747_928_video_HDMI.dtbo
imx6qdl-seco_quadmo747_928_video_LVDS_HDMI.dtbo
imx6qdl-seco_quadmo747_928_video_HDMI_LVDS.dtbo

...

962

...

μQ7

...

HDMI,

LVDS

...

imx6qdl-seco_uq7_962_video_LVDS.dtbo
imx6qdl-seco_uq7_962_video_LVDSx2_CLONE.dtbo
imx6qdl-seco_uq7_962_video_LVDSx2_DUAL.dtbo
imx6qdl-seco_uq7_962_video_HDMI.dtbo
imx6qdl-seco_uq7_962_video_LVDS_HDMI.dtbo
imx6qdl-seco_uq7_962_video_HDMI_LVDS.dtbo

...

A75-J

...

μQ7

...

HDMI,

LVDS

...

imx6qdl-seco_uQ7_J_A75_video_LVDS.dtbo
imx6qdl-seco_uQ7_J_A75_video_LVDSx2_CLONE.dtbo
imx6qdl-seco_uQ7_J_A75_video_LVDSx2_DUAL.dtbo
imx6qdl-seco_uQ7_J_A75_video_HDMI.dtbo
imx6qdl-seco_uQ7_J_A75_video_LVDS_HDMI.dtbo
imx6qdl-seco_uQ7_J_A75_video_HDMI_LVDS.dtbo

...

A62-J

...

SBC

...

HDMI,

LVDS,

Sitronix touch(st1232),

Goodix Touch(gt928)

...

imx6qdl-seco_SBC_A62_touch_gt928.dtbo
imx6qdl-seco_SBC_A62_touch_st1232.dtbo
imx6qdl-seco_SBC_A62_video_LVDS.dtbo
imx6qdl-seco_SBC_A62_video_LVDSx2_CLONE.dtbo
imx6qdl-seco_SBC_A62_video_LVDSx2_DUAL.dtbo
imx6qdl-seco_SBC_A62_video_HDMI.dtbo
imx6qdl-seco_SBC_A62_video_LVDS_HDMI.dtbo
imx6qdl-seco_SBC_A62_video_HDMI_LVDS.dtbo

...

B08

...

SBC & SYS

...

LVDS,

RGB

...

imx6sx-seco_SBC_B08_LVDS.dtbo
imx6sx-seco_SBC_B08_RGB.dtbo

...

C23

...

SBC

...

LVDS

...

imx6sx-seco_SBC_C23_LVDS.dtbo

In Linux BSP 9.0 you can list these files available on the boot partition,

For eg: A62

ls -l boot/
total 8532
-rw-r--r-- 1 secospa secospa   69897 Sep 16 13:17 imx6dl-seco_SBC_A62.dtb
-rw-r--r-- 1 secospa secospa      72 Sep 16 13:17 imx6qdl-seco_SBC_A62_conn_j8.dtbo
-rw-r--r-- 1 secospa secospa     307 Sep 16 13:17 imx6qdl-seco_SBC_A62_touch_gt928.dtbo
-rw-r--r-- 1 secospa secospa     311 Sep 16 13:17 imx6qdl-seco_SBC_A62_touch_st1232.dtbo
-rw-r--r-- 1 secospa secospa     942 Sep 16 13:17 imx6qdl-seco_SBC_A62_video_HDMI.dtbo
-rw-r--r-- 1 secospa secospa    1556 Sep 16 13:17 imx6qdl-seco_SBC_A62_video_HDMI_LVDS.dtbo
-rw-r--r-- 1 secospa secospa     812 Sep 16 13:17 imx6qdl-seco_SBC_A62_video_LVDS.dtbo
-rw-r--r-- 1 secospa secospa    1556 Sep 16 13:17 imx6qdl-seco_SBC_A62_video_LVDS_HDMI.dtbo
-rw-r--r-- 1 secospa secospa     955 Sep 16 13:17 imx6qdl-seco_SBC_A62_video_LVDSx2_CLONE.dtbo
-rw-r--r-- 1 secospa secospa    1088 Sep 16 13:17 imx6qdl-seco_SBC_A62_video_LVDSx2_DUAL.dtbo
-rw-r--r-- 1 secospa secospa   71563 Sep 16 13:17 imx6q-seco_SBC_A62.dtb

Once done, you can boot the board using seco_config tool to configure the Device tree overlay, Below are the commands to setup,

...

           IPU_PIX_FMT_YUYV
    UYVY            IPU_PIX_FMT_UYVY
    YVYV            IPU_PIX_FMT_YVYU
    VYUY            IPU_PIX_FMT_VYUY

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.
Starting from the above structure (data timings structure), edit the sub-structure "mode" by considering the following fields:

}, {
        .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,
                .yres           = 800,
                .pixclock       = 15128,
                .left_margin    = 220,
                .right_margin   = 40,
                .upper_margin   = 21,
                .lower_margin   = 7,
                .hsync_len      = 60,
                .vsync_len      = 10,
              

...

...

...

.

...

LVDS Customization Guide for i.MX8

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 pane

The SECO boards with i.MX8 SoC supports MIPI-DSI interface,

• Texas Instruments SN65DSI84 MIPI® DSI bridge to FlatLink™ LVDS single-channel DSI to dual-link LVDS bridge

• Texas Instruments SN65DSI86 Dual-channel MIPI® DSI to embedded DisplayPort™ (eDP ) bridge.

DCSS vs LCDIF

i.MX8M boards comes with 2 display controllers: DCSS and LCDIF.

1. DCCS can be connected to HDMI, DP or MIPI-DSI and supports resolutions up to 4K.

2. LCDIF can be connected only to MIPI-DSI and supports resolutions up to 1080p..

All drivers on the i.MX8,i.MX8M Mini,i.MX8M Nano,i.MX8X and i.MX8M Plus family modules are integrated into the Linux kernel's DRM/KMS subsystem.

Display Interface should be added in the Linux Device Tree overlay and Panel 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 the overlay through *.dtbo file.

To obtain information about overlay device tree, you can refer to the documentation presents into the kernel:

linux-seco/Documentation/devicetree/overlay-notes.txt

Using the above document you can customize the device tree overlay enable and disable functionality.

Embedded displays often do not have a dedicated DDC (e.g. parallel RGB, LVDS, or similar display links), and therefore the system needs to be told what exact display resolution and timings have to be supplied.

Embedded displays without DDC channel (parallel RGB/LVDS) use a fixed mode provided by the driver, this can be either:

• display modes from a display driver (used for kernel mode settings (KMS) e.g. from panel-simple.c, e.g. i.MX8 DRM driver);

• display modes from a specific devicetree overlay (support available just from BSP 9 on);

• KMS interface (Kernel Mode Setting, part of the Direct Rendering Manager (DRM) interface, kernel argument, through Xorg/RandR using modesetting driver).

Adding Custom LVDS support in panel-simple.c for i.MX8*

The connected panel is represented in the device tree in its own node. That node references the used LDB/LVDS channel through its node 'port'.One can either use the panel-simple or the panel-lvds driver, both options are outlined below.

Panel Simple

Set the property 'compatible'

sync           = 0,
                .vmode          = FB_VMODE_NONINTERLACED
        }
  }, {
        .bus    = -1,
        .addr   = -1,
        .pixfmt = IPU_PIX_FMT_RGB24,
        .detect = NULL,
        .enable = enable_lvds,
        .mode   = {
                // new data structure 
                .name           = "NEW CUSTOM RESOLUTION",
                .refresh        = <custom refresh>,
                .xres           = <custom horiz. resolution>,
                .yres           = <custom vert. resolution>,
                .pixclock       = <pixel clock in us>,
                .left_margin    = <horiz. back porch>,
                .right_margin   = <horiz. front porch>,
                .upper_margin   = <vert. back porch>,
                .lower_margin   = <vert. front porch>,
                .hsync_len      = <horiz. SYNC lenght>,
                .vsync_len      = <vert. SYNC lenght>,
                .sync           = 0,
                .vmode          = FB_VMODE_NONINTERLACED
        }

4. Boot with new resolution

• Set the right resolution at U-Boot:

setenv panel "<resolution name>
saveen

• Set the right resolution at kernel, using seco_config command:

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]
8) NEW_RESOLUTION
> 8

...

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

...

Display Customization Guide for i.MX8

The MIPI DSI support on i.MX8-based boards is configured via the overlays device trees and Kernel sources.

SECO boards with i.MX8 SoC support the following MIPI-DSI interface to LVDS / eDP bridges:

• Texas Instruments SN65DSI84 MIPI^® DSI bridge to FlatLink™ LVDS single-channel DSI to dual-link LVDS bridge;

• Texas Instruments SN65DSI86 Dual-channel MIPI^® DSI to embedded DisplayPort™ (eDP ) bridge.

DCSS vs eLCDIF

i.MX8M boards come with 2 display controllers, DCSS and eLCDIF:

1. DCCS can be connected to HDMI, DP or MIPI-DSI and supports up to 4K resolution;

2. eLCDIF can be connected only to MIPI-DSI and supports up to 1080p resolution.

Adding Custom LVDS / eDP panel support in panel-simple.c for i.MX8

The panel is configured by the following nodes located in the board device tree, for example arch/arm64/boot/dts/seco/seco-imx8mm-c61.dts:

panel_edp: edp_panel {
      compatible = "boe,ev156fhm";
      #address-cells = <1>;
      #size-cells = <0>;
};

panel_lvds: lvds_panel {
      compatible = "auo,p215hca-high";
      #address-cells = <1>;
      #size-cells = <0>;
};

These nodes represent the links between the device tree and the panel-simple.c structure through the compatibleproperty to an existing or newly added panel from the panel-simple driver.

linux-seco/drivers/gpu/drm/panel/panel-simple.c

To obtain information about panel-simple.txt, you can refer to the documentation presents into the kernel:

linux-seco/Documentation/devicetree/bindings/display/panel/simple-panel.txt

To configure custom display timing for  AUO Panel model p215

The kernel writes Timing in panel-simple.c and directly matches with short strings. There are the following statements in the drivers/gpu/drm/panel/panel-simple.c file

static const struct display_timing auo_p215hca_high_timing = {/panel/panel-simple.c

Example: Configure the custom display timing for AUO Panel model p215hca

In SECO BSP's the references panels are configured and tested with 10000 on/off cycle. Below is the panel structure from drivers/gpu/drm/panel/panel-simple.c for LVDS 1920x1080 from SECO BSP9:

static const struct display_timing auo_p215hca_high_timing = {
        .pixelclock = { 139000000, 160000000, 165000000 },
        .hactive = { 1920, 1920, 1920 },
        .hfront_porch = { 1, 85, 90 },
        .hsync_len = { 1, 10, 45 },
        .hback_porch = { 1, 85, 150 },
        .vactive = { 1080, 1080, 1080 },
        .pixelclockvfront_porch = { 1390000003, 16000000020, 16500000050 },
        .hactivevsync_len = { 19206, 192010,60 1920 },
        .hfrontvback_porch = { 111, 8520, 9037 },
        .hsync_len = { 1, 10, 45 },flags = DISPLAY_FLAGS_HSYNC_LOW |
                   .hback_porch = { 1, 85, 150 },DISPLAY_FLAGS_VSYNC_LOW |
                 .vactive = { 1080, 1080, 1080 }, DISPLAY_FLAGS_DE_LOW |
           .vfront_porch = { 3, 20, 50 },  DISPLAY_FLAGS_PIXDATA_NEGEDGE,
};

static const struct  .vsync_lenpanel_desc auo_p215hca_high = {
6, 10,60  },     .timings =   .vback_porch = { 11, 20, 37 }&auo_p215hca_high_timing,
        .num_timings = 1,
        .flagsbpc = DISPLAY_FLAGS_HSYNC_LOW |8,
        .size = {
         DISPLAY_FLAGS_VSYNC_LOW |      .width = 68,
           DISPLAY_FLAGS_DE_LOW |    .height = 121,
        },
    DISPLAY_FLAGS_PIXDATA_NEGEDGE, };  static const struct panel_desc auo_p215hca_high .delay = {
        .timings = &auo_p215hca_high_timing,        /*
     .num_timings = 1,         .bpc =* 8,The panel spec recommends one second delay
  .size = {             * to the below items.width = 68However, it's a bit too
             .height = 121,  * long in pratical.  Based on }tests, it turns
      .delay = {         * out 100 milliseconds is fine.
  /*               */
      * The panel spec recommends one second delay   .prepare = 100,
            * to the below items.enable = However100,
it's a bit too             .unprepare = 100,
  * long in pratical.  Based on tests, it turns     .disable = 100,
        },
  *  out 100 milliseconds is fine.bus_format = MEDIA_BUS_FMT_RGB888_1X24,//MEDIA_BUS_FMT_RGB888_1X7X4_SPWG,
};

static const struct of_device_id platform_of_match[] = {
	{
    }, */{
                .preparecompatible = 100"auo,p215hca-high",
                .enabledata = 100&auo_p215hca_high,
       }, {
		/* sentinel */
    .unprepare = 100,
                .disable = 100,
  	}
};

In this case the configured panel is the: auo,p215hca-high. All the parameters configured in struct display_timing are derived from the panel datasheet.

After setting up the panel configuration, you need to check the following file for the LVDS (for the eDP this section can be skipped):

linux-seco/arch/arm64/boot/dts/seco/overlays/seco-imx8mm-c61-lcdif-sn65dsi84-overlay.dts

This is the content:

target = <&adv_bridge>;
      __overlay__ {
     },         .bus_format#address-cells = MEDIA_BUS_FMT_RGB888_1X24,//MEDIA_BUS_FMT_RGB888_1X7X4_SPWG,
};

static const struct of_device_id platform_of_match[] = {
	{<1>;
              }, {
#size-cells = <0>;
              lvds,datamap .compatible = "auo,p215hca-high",jeida";
              lvds,dual-channel;
    .data = &auo_p215hca_high,        }lvds, {
		/* sentinel */
	}
};
MODULE_DEVICE_TABLE(of, platform_of_match);

MODULE_DEVICE_TABLE(of, platform_of_match); The timing parameters are configured in the structure

auo,p215hca-high.

After the timing parameter need to call the device tree file with compatible device on the panel.

Please refer the respective SECO boards device tree (.dts)file.

For eg: SECO-imx8MM-c72.dts

panel_lvds: lvds_panel {
		compatible = "auo,p215hca-high";
		#address-cells = <1>;
		#size-cells = <0>;
	};

Most of the i.MX8 is configured in SN65DSI84 Bridge for LVDS, so you can find the Device tree overlay to enable and disable the display file without disturbing main device tree.

linux-seco/arch/arm64/boot/dts/seco/overlays/seco-imx8mm-c72-lcdif-sn65dsi84-overlay.dts

In below some pre-built device tree overlay file for i.MX8 boards and listed Once you done the setup , you can compile the kernel with added LVDS display resolution. after the compilation please copy the file into device and boot the board and setting up the custom device tree file with support of seco_config file.

Device tree display overlay for i.MX8

...

Board

...

Module

...

Peripheral

...

Overlays

...

C12

...

SMARC

...

MIPI-DSI to LVDS,

HDMI

...

seco-imx8mq-c12-lcdif-sn65dsi84.dtbo
seco-imx8mq-c12-dcss-sn65dsi84.dtbo
seco-imx8mq-c12-dual-display.dtbo
seco-imx8mq-c12-hdmi.dtbo
seco-imx8mq-c12-dcss-sn65dsi84-800x480.dtbo

...

C20

...

SBC

...

MIPI-DSI to LVDS,

HDMI

...

seco-imx8mq-c20-hdmi.dtbo
seco-imx8mq-c20-edp.dtbo
seco-imx8mq-c20-dcss-sn65dsi84.dtbo

...

C25

...

Q7

...

MIPI-DSI to LVDS,

MIPI-DSI to eDP,

HDMI

...

seco-imx8mq-c25-hdmi.dtbo
seco-imx8mq-c25-dcss-sn65dsi84.dtbo
seco-imx8mq-c25-dcss-sn65dsi84-800x480.dtbo
seco-imx8mq-c25-dcss-sn65dsi86.dtbo
seco-imx8mq-c25-dp.dtbo

...

C26

...

Q7

...

LVDS,

DP,

HDMI

...

seco-imx8qm-c26-hdmi.dtbo
seco-imx8qm-c26-dp.dtbo
seco-imx8qm-c26-lvds-single.dtbo
seco-imx8qm-c26-lvds-dual.dtbo
seco-imx8qm-c26-hdmi-lvds.dtbo
seco-imx8qm-c26-dp-lvds.dtbo
seco-imx8qm-c26-hdmiin.dtbo

...

C43

...

SBC

...

MIPI-DSI to eDP,

LVDS,

HDMI

...

seco-imx8qm-c43-hdmi.dtbo
seco-imx8qm-c43-hdmi-lvds.dtbo
seco-imx8qm-c43-dp-lvds.dtbo
seco-imx8qm-c43-sn65dsi86.dtbo
seco-imx8qm-c43-hdmi-sn65dsi86.dtbo
seco-imx8qm-c43-hdmi-lvds-sn65dsi86.dtbo
seco-imx8qm-c43-lvds-single.dtbo
seco-imx8qm-c43-lvds-dual.dtbo
seco-imx8qm-c43-hdmiin.dtbo

...

C72

...

μQ7

...

MIPI-DSI to LVDS,

MIPI-DSI to eDP

...

seco-imx8mm-c72-lcdif-sn65dsi84.dtbo
seco-imx8mm-c72-lcdif-sn65dsi86.dtbo

...

C61

...

SBC

...

MIPI-DSI to LVDS,

MIPI-DSI to eDP

...

seco-imx8mm-c61-lcdif-sn65dsi86.dtbo
seco-imx8mm-c61-lcdif-sn65dsi84.dtbo

...

C57

...

SBC

...

MIPI-DSI to eDP,

LVDS

...

seco-imx8qxp-c57-800x600-lvds.dtbo
seco-imx8qxp-c57-1280x800-lvds.dtbo
seco-imx8qxp-c57-1920x1080-dual-channel-lvds.dtbo
seco-imx8qxp-c57-1920x1200-dual-channel-lvds.dtbo
seco-imx8qxp-c57-sn65dsi86-edp.dtbo
seco-imx8qxp-c57-sn65dsi86-edp.dtbo

...

D16

...

SMARC

...

MIPI-DSI to eDP,

LVDS,

HDMI

...

seco-imx8qxp-d16-sn65dsi86-edp.dtbo
seco-imx8qxp-d16-adv7535-hdmi.dtbo
seco-imx8qxp-d16-lvds0-single.dtbo
seco-imx8qxp-d16-lvds0-dual.dtbo
seco-imx8qxp-d16-hdmi-edp.dtbo

...

channel-swap;
              lvds,preserve-dsi-timings;
                                      /*include/drm/drm_mipi_dsi.h*/
              dsi,mode-flags = <0x805>; /*MIPI_DSI_MODE_VIDEO*/
              clocks = <&si5351a 0>;
              status = "okay";
        };

To complete the bridge configuration, it is necessary to correctly configure the following parameters:

• lvds,datamap: can be configured as jeida or spwg, other configurations are not supported.

• lvds,dual-channel:if inserted, it enables bridge dual channel output. The DSI video signal is splitted in LVDS channel A and LVDS channel B.

• lvds,preserve-dsi-timings:this parameter is useful when the LVDS display timing is synchronized with Data Enable, while it should be removed if the panel is not DE sync. LVDS panels 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.

SECO preconfigured Panels

Below are some pre-built Device Tree Overlay files for i.MX8-based boards.

Once the setup has been defined, the Kernel, including LVDS display resolution, can be built. After compiling, please copy the file into the device and boot the board by setting up the custom device tree file with the support of seco_config file.

Device tree display overlay for i.MX8

In Linux BSP 9.0, you can list these the available files available on the boot partition,.

For eg: C72example, with the SBC-C61:

ls -l boot/
total 25604
-rw-r--r-- 1 secospa secospa 26073600 Sep 16 02:55 Image
-rw-r--r-- 1 secospa secospa     6000 Sep 16 02:55 imx8mm_m4_TCM_hello_world.bin
-rw-r--r-- 1 secospa secospa    16528 Sep 16 02:55 imx8mm_m4_TCM_rpmsg_lite_pingpong_rtos_linux_remote.bin
-rw-r--r-- 1 secospa secospa    16028 Sep 16 02:55 imx8mm_m4_TCM_rpmsg_lite_str_echo_rtos.bin
-rw-r--r-- 1 secospa secospa    40092 Sep 16 02:55 imx8mm_m4_TCM_sai_low_power_audio.bin
-rw-r--r-- 1 secospa secospa    53688 Sep 16 02:55 seco-imx8mm-c72c61.dtb
-rw-r--r-- 1 secospa secospa     2140 Sep 16 02:55 seco-imx8mm-c72c61-lcdif-sn65dsi84.dtbo
-rw-r--r-- 1 secospa secospa     1797 Sep 16 02:55 seco-imx8mm-c72c61-lcdif-sn65dsi86.dtbo

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

Below are the commands to for the setup,:

u-boot seco c72c61=> seco_config
__________________________________________________
Choose boot Device for Kernel.
__________________________________________________
1) eMMC onboard
2) uSD onboard
3) TFTP
4) USB
> 1
Choose the partition
> 1
Path of the Kernel (enter for default Image) >
__________________________________________________
Choose boot Device for FDT.
__________________________________________________
1) eMMC onboard
2) uSD onboard
3) TFTP
4) USB
> 1
Choose the partition
> 1
Path of the FDT (enter for default seco-imx8mqimx8mm-c12c61.dtb) >
__________________________________________________
Choose boot Device for FileSystem.
__________________________________________________
1) eMMC onboard
2) uSD onboard
3) NFS
4) USB
> 1
Choose the partition
> 2
__________________________________________________
Choose Video Output Configuration.
__________________________________________________
1) no video - no dtbo
2) eDP LCDIF-1920x1080 - seco-imx8mm-c72c61-lcdif-sn65dsi86.dtbo
3) LVDS LCDIF-1920x1080 - seco-imx8mm-c72c61-lcdif-sn65dsi84.dtbo
> 2
__________________________________________________
Choose Board Options.
__________________________________________________
1) No addons
> 1
Saving Environment to MMC... Writing to MMC(0)... OK

By selecting the dtbo to perform the board boot up The board will boot with your display configuration.

...