Imx8 configure mipi-dsi, the screen does not display（Q10.0.0_2.2.0_AUTO）

[relax-wu]

SDK：Q10.0.0_2.2.0_AUTO

lunch mek_8q_car-userdebug

mipi-->ds90ub941-->ds90ub948-->lvds

Mipi-dsi is configured in Android
The rear_view_camera demo is used, which is also configured as mipi-dsi.
The mipi signal waveform cannot be measured with an oscilloscope.

When lunch mek_8q_car2-userdebug, the display is normal, and the waveform signal can be measured with an oscilloscope

[jimmychan]

Could you tell me which board are you using?

Yes, there are different between mek_8q_car and mek_8q_car2. Please read the Android User's Guide.pdf Chapter 8.10 for more details.

[relax-wu]

And M4 log

[relax-wu]

I am using MCIMX8QXP-CPU (MEK), I currently only configure mipi-dsi, the attachment is my modification, and log

[jimmychan]

"When lunch mek_8q_car2-userdebug, the display is normal".

Could you send me the log of the normal one?

Thanks.

[relax-wu · Accepted solution]

I have solved the problem, but I don’t know if this is completely correct

Observe the printing information and notice this abnormal printing

[ 1.318608] imx-drm display-subsystem: parent device of /bus@56220000/dsi_host@56228000 is not available
[ 1.328133] imx-drm display-subsystem: parent device of /bus@56220000/dsi_host@56248000 is not available

Find the corresponding code: vendor/nxp-opensource/kernel_imx/drivers/gpu/drm/drm_of.c

drm_of_component_probe_with_match is called by vendor/nxp-opensource/kernel_imx/drivers/gpu/drm/imx/imx-drm-core.c

drm_of_component_probe_with_match

    port = of_parse_phandle(dev->of_node, "ports", i);

    for_each_child_of_node(port, ep) {

        remote = of_graph_get_remote_port_parent(ep);

        if (!remote || !of_device_is_available(remote)) {

            of_node_put(remote);

            continue;

        } else if (!of_device_is_available(remote->parent)) {

            dev_warn(dev, "parent device of %pOF is not available\n",

                    remote);

            of_node_put(remote);

            continue;

        }

        drm_of_component_match_add(dev, &match, compare_of,

                           remote);

        of_node_put(remote);

    }

    of_node_put(port);

Add printing information and find that the value of remote is as follows

/bus@56220000/ldb@562210e0/lvds-channel@0             The device tree is disabled

/bus@56220000/ldb@562210e0/lvds-channel@1             The device tree is disabled

/bus@56220000/dsi_host@56228000

/bus@56220000/ldb@562410e0/lvds-channel@0             The device tree is disabled

/bus@56220000/ldb@562410e0/lvds-channel@1             The device tree is disabled

/bus@56220000/dsi_host@56248000

The parent node of /bus@56220000/dsi_host@56228000 and /bus@56220000/dsi_host@56248000 is lvds_subsys shared by M4. At the beginning, it was disabled, so an error was reported. It also causes that when Android starts, when bind is executed, there is no dsi_host node, and no display

The official default is LVDS. The parent node of /bus@56220000/ldb@562210e0/lvds-channel@0 is ldb1, which is okay by default, so there is no problem.

So you should set display_subsystem to disabled, and then add it to the M4 share. Modify as follows:

--- a/vendor/nxp-opensource/kernel_imx/arch/arm64/boot/dts/freescale/imx8qxp-ss-dc.dtsi

+++ b/vendor/nxp-opensource/kernel_imx/arch/arm64/boot/dts/freescale/imx8qxp-ss-dc.dtsi

@@ -41,7 +41,7 @@

};

/ {

-       display-subsystem {

+       display_subsystem: display-subsystem {

                compatible = "fsl,imx-display-subsystem";

                ports = <&dpu_disp0>, <&dpu_disp1>;

        };

--- a/vendor/nxp-opensource/kernel_imx/arch/arm64/boot/dts/freescale/imx8qxp-mek-car.dts

+++ b/vendor/nxp-opensource/kernel_imx/arch/arm64/boot/dts/freescale/imx8qxp-mek-car.dts

@@ -26,12 +26,17 @@

        status = "disabled";

};

+&display_subsystem {

+       status = "disabled";

+};

+

&vehicle_rpmsg_m4 {

        #address-cells = <2>;

        #size-cells = <2>;

        status = "okay";

        ranges;

        fsl,resources = <&lvds_subsys>,

+                       <&display_subsystem>,

                        <&dc0_subsys>,

                        <&img_subsys>;