Enabling multiple-display function on iMX8QM 2 for A-core & 2 for M-core

[Jose1985]

Dear Team,

SW: Android Automotive 13.0.0_1.1.0

HW: iMX8QM MEK

Application core : Android

M4 core              : Free RTOS

Please refer the below table.

I need to run below requirements simultaneously.

Requirement 1:  I need to drive 2 displays from Android (LVDS0_CH0, MIPI_DSI1)

Requirement 2:  I need to drive 2 displays from FreeRTOS (HDMI_TX,  LVDS1_CH0)

Is it possible? If so, can you help with the changes required.

Reference : 8.3.2 Enabling multiple-display function

Board	Number of displays	Display port
i.MX 8QuadMax MEK	4	HDMI_TX, LVDS0_CH0, LVDS1_CH0, MIPI_DSI1
Optional	4	LVDS0_CH0 and LVDS1_CH0, MIPI_DSI0 and MIPI_DSI1

Best regards

Jose.

[Jose1985]

Hi @Sanket_Parekh ,

Any update?

best regards

Jose

[Sanket_Parekh]

Hello @Jose1985 

I hope you are doing well.

Yes, it is possible to drive two displays from Android and two displays from FreeRTOS simultaneously. 
->Please make sure that the displays must be connected to different video ports. One cannot connect both displays to the same video port.
->Please make sure that the displays must be configured to use different resolutions and refresh rates. One cannot configure both displays to use the same resolution and refresh rate.
->Please make sure that the displays must be driven by different CPUs.(one by A-core & one by M-core) One cannot drive both displays from the same CPU.

I hope this information helps!

Thanks & Regards,

Sanket Parekh

[Jose1985]

Dear @Sanket_Parekh ,

Thank you for confirming. However, I need the details from DTS file point of view

Could you let me know what is the combination of DPU's to port mapping? DPU1 mapped to which ports and DPU2 mapped to which ports?

This is our detailed requirement:

Android runs on 6 A-core (2 A-73 & 4 A-53) : I want to drive LVDS-0 (1920x1080) & MIPI-0 (1920x720) from Android

FreeRTOS run on 2 M4-core : I want to drive LVDS-1 (800x400) & HDMI Tx/MIPI-1 (800x400) from FreeRTOS

Could you help me with the DTS modification that I need to do in Android kernel to enable only LVDS0 & MIPI0 ?

Best regards,

Jose

[Sanket_Parekh]

Hello @Jose1985 

I hope you are doing well.

Please find the example given below for the same.
Please refer to it.

&mipi0_disp {
    compatible = "fsl,imx8mp-mipi-display";
    disp-type = "mipi-dsi";
    status = "okay";
    port@0 {
        endpoint {
            remote-endpoint = <&dpu1_mipi0>;
        };
    };
};

&lvds0_disp {
    compatible = "fsl,imx8mp-lvds-display";
    disp-type = "lvds";
    status = "okay";
    port@0 {
        endpoint {
            remote-endpoint = <&dpu1_lvds0>;
        };
    };
};

For more details please refer to the location given below.
Documentation/devicetree/bindings/display/

Thanks & Regards,

Sanket Parekh

[Jose1985]

Dear @Sanket_Parekh ,

I tried following points :

• Android disable LVDS1 from DTS file of Android Linux kernel ==> Successful, now Android display only from LVDS0
• FreeRTOS shows camera view from CSI0 (OV5640) on LVDS1 as soon as boot up => Successful

However, when Android boots up, for some reason the display/camera goes down and the LVDS1 screen is blank. We suspect that there is some thing happening at vehicle_rpmsg_m4 driver is doing something without any specific logs.  Do you have any idea why it happens?

Our requirement is to

1. Show camera CSI0 view on LVDS1 display driven by FreeRTOS ==> Not successful after Androdi boots.
2. Show Android UI/UX on LVDS0 ==> Successful

Best regards

Jose

[Sanket_Parekh]

Hello @Jose1985 ,

I hope you are doing well.

->Please make sure to check the CSI0 configuration, also check the csi0 is being used by m-4 only.
->If one is capturing it by a-53 and then passing it by rpmsg to m4.
->Please share the CSI0 configurations.

Thanks & Regards,
Sanket Parekh

[Jose1985]

Dear @Sanket_Parekh ,

LVDS1 & CSI0 is initially used by M4 core by rear_view_camera app.

However, when Androdi boots up vehicle_rpmsg_m4 driver inserts fsl,resource such as &lvds1_subsys, &dc1_subsys & img0_subsys from notice_evs_release.

My question is,

1. What is dc1_subsys0? is it power domain?
2. I dont want to enable lvds* node, but only mipi-dsi0 for Android.
3. We believe img0_subsys is for camera and removing it from vehicle_rpmsg_m4 DTS node shall remove camera being up in A-core

Could you please let me know which node to enable for MIPI-DSI0 in DTS file so that vehicle_rpmsg_m4 doesn't affect LVDS1 output from m4?

Best regards

Libin Jose

[Sanket_Parekh]

Hello @Jose1985 ,

I hope you are doing well.
Please accept my apology for the delayed response.

->DC1_subsys0 is a power domain that controls the MIPI-DSI0 controller.
->LVDS1 controller is controlled by the lvds1_subsys node.

&mipi_dsi0 {
compatible = "fsl,imx8qm-mipi-dsi";
status = "okay";
};
This will enable the MIPI-DSI0 controller and allow Android to use it. The LVDS1 controller will not be affected by this change.

I hope this helps!

Thanks & Regards,
Sanket Parekh

[Jose1985]

Dear @Sanket_Parekh ,

It doesnt seems to work. Can you please let me know how can we enable all.display for Android. this means I need 4 displays lvds0, lvds1, dsi0 & dsi1.

Best regards

Jose

[Sanket_Parekh]

Hello @Jose1985 ,

I hope you are doing well.

"It doesn't seems to work. Can you please let me know how can we enable all? display for Android. this means I need 4 displays lvds0, lvds1, dsi0 & dsi1"
->Please check the all the port nodes in the device tree are enabled or not.
If not then please make it okay instead of disabled.
status="okay"

The driver for the LVDS panel is drivers/gpu/drm/panel/panel-simple.c
Therefore one needs to enable CONFIG_DRM_PANEL_SIMPLE=y in the defconfig.

I hope it helps!

Thanks & Regards,
Sanket Parekh

[Jose1985]

Dear Sanket,

I tried this option but for Android the display is coming from LVDS0_CH0 (Primary) and LVDS1_CH0 (Secondary).

But my requirement is slightly different:

For Android, I need LVDS0_CH0 & MIPI_DSI0 

For RTOS, I need LVDS1_CH0 & HDMI

Is this combination possible? Basically, I need to drive 2 display from Android simultaneously and 2 display from FreeRTOS

Best regards

Jose

[Sanket_Parekh]

Hello @Jose1985 

I hope you are doing well.

->Please refer to section 8.3.2 Enabling multiple-display function in the Android user guide.
https://www.nxp.com/docs/en/user-guide/ANDROID_USERS_GUIDE.pdf?_gl=1*hcjvrf*_ga*NDkxMzM1NzM0LjE2ODY3.....

I hope this information helps!

Thanks & Regards,

Sanket Parekh