STM32 board support eDP bridge?

[LLe.1]

Hi,

We are using stm32mp157c MCU/board and it has DSI output built-in. Now we want to add display port support via DSI to eDP bridge SN65DSI86. It seems that stm32 does not support Displayport output or it has never been done. At least the driver dw_mipi_dsi-stm.c should be updated not to require a panel.

Any idea how this can be achieved please?

[Erwan SZYMANSKI]

Hello @LLe.1​,

Can you tell me on which OSTL version are you actually working on ?

Did you take a look at modifications that came with OSTL 4.0 ? A lot of modifications have been made on this particular TI bridge driver for DSI to eDP feature.

Regards.

Erwan.

[Erwan SZYMANSKI]

@LLe.1​ ,

Regarding at the TI-SN65DSI86 bridge, it seems that there is no obvious blocker to use it.

As an example of another bridge that links DSI and a connector, you can look at DSI-HDMI bridge AVD7533.

Concerning this TI bridge, it is capable of working with burst or non-burst mode. We advise you to work with burst mode which is easier to put in place.

You will have to use YAML documentation to configure all the device tree port etc...

Instead of attaching a panel to the DSI, you will have to attach the entry of your bridge, itself attached to your eDP connector.

Note that the STM32MP157C has 2 DSI physic lanes, so you will not be able to have a full HD resolution in output.

Regards.

Erwan.

[LLe.1]

Thanks @Erwan SZYMANSKI​ for the quick reply. I am surprise and appreciate it deeply.

Im using ostl version 3.1.8 linux kernel version 5.4.31. Should I do an upgrade or it is enough?

Below is my device tree, it seems DSI driver does not see all prerequisites and thus does not start communicating.

#include <dt-bindings/input/ti-drv260x.h>
 
/ {
 
        panel: panel {
                compatible = "lg,lp120up1";
                power-supply = <&v3v3>;
                status = "okay";
                backlight = <&backlight>;
                port {
                                edp_panel_in: endpoint {
                                                remote-endpoint = <&edp_bridge_out>;
                                };
 
                };
        };
 
 
};
 
&i2c2 {
 
        edp_bridge: edp_bridge@2c {
                status = "okay";
                compatible = "ti,sn65dsi86";
                #address-cells = <1>;
                #size-cells = <0>;
                reg = <0x2c>;
 
                enable-gpios = <&gpiob 9 GPIO_ACTIVE_HIGH>;
 
                vccio-supply = <&v1v8_reg>;
                vcca-supply = <&v1v2_reg>;
                vpll-supply = <&v1v8_reg>;
                vcc-supply = <&v1v2_reg>;
 
                clock-names = "refclk";
                clocks = <&input_refclk>;
 
                ports {
                        #address-cells = <1>;
                        #size-cells = <0>;
 
                        port@0 {
                                reg = <0>;
 
                                edp_bridge_in: endpoint {
                                                remote-endpoint = <&dsi_out>;
                                };
                        };
 
                        port@1 {
                                reg = <1>;
                                edp_bridge_out: endpoint {
                                                data-lanes = <0 1>;
                                                lane-polarities = <0 0>;
                                                remote-endpoint = <&edp_panel_in>;
                                };
                        };
                };
 
        };
};
 
 
&dsi {
        #address-cells = <1>;
        #size-cells = <0>;
        status = "okay";
 
        ports {
                #address-cells = <1>;
                #size-cells = <0>;
 
                port@0 {
                        reg = <0>;
                        dsi_in: endpoint {
                                remote-endpoint = <&ltdc_ep0_out>;
                        };
                };
 
                port@1 {
                        reg = <1>;
                        dsi_out: endpoint {
                                remote-endpoint = <&edp_bridge_in>;
                                data-lanes = <0 1 2 3>;
                                attach-bridge;
                        };
                };
        };
 
};
 
&ltdc {
        status = "okay";
 
        port {
                #address-cells = <1>;
                #size-cells = <0>;
 
                ltdc_ep0_out: endpoint@0 {
                        reg = <0>;
                        remote-endpoint = <&dsi_in>;
                };
        };
};

[Erwan SZYMANSKI]

Hi @LLe.1​,

As far as I am concerned, I would advise you to up to OSTL 4.0, to avoid any backport from 4.0 to 3.1 if needed. But this is just in prevention, maybe you will be able to do everything you want without any problem with 3.1. It is up to you !

Having a quick look at your device tree, as I said our DSI has only 2 lanes. I think you will have to replace:

"data-lanes = <0 1 2 3>" by "data-lanes = <0 1>"

Can you put me maybe some logs where you have errors that can help me to debug with you ?

Regards.

Erwan.

[LLe.1]

@Erwan SZYMANSKI​  that would be so kind of you willing to help debug this.

It does not print any error message out but I have my own debug logs and it seems like dsi-stm driver is still searching for panel instead of bridge for some reason. And as there is no panel, dsi does not start its operation.

(All ERRORs below are my own debug logs)

root@myPOD:~# dmesg | grep ERROR
 
[  1.038038] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi probe
 
[  1.041566] [drm:panel_simple_probe] *ERROR* start to add panel
 
[  1.122729] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi probe
 
[  1.124892] [drm:panel_simple_probe] *ERROR* start to add panel
 
[  1.149027] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi probe
 
[  1.151215] [drm:panel_simple_probe] *ERROR* start to add panel
 
[  1.217838] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi probe
 
[  1.219367] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  1.219416] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  1.220582] [drm:panel_simple_probe] *ERROR* start to add panel
 
[  1.320740] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi probe
 
[  1.326817] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  1.331672] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  1.339546] [drm:panel_simple_probe] *ERROR* start to add panel
 
[  1.947582] [drm:ti_sn_bridge_probe] *ERROR* probe bridge
 
[  1.951675] [drm:ti_sn_bridge_probe] *ERROR* check i2c ok, proceed
 
[  1.957926] [drm:ti_sn_bridge_probe] *ERROR* init i2c client ok
 
[  1.963739] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  1.969819] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  1.976564] [drm:ti_sn_bridge_probe] *ERROR* panel node step 1 nOK, err code: -517
 
[  2.115607] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi probe
 
[  2.120864] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi start generic dsi probe
 
[  2.128194] [drm:__dw_mipi_dsi_probe] *ERROR* DW: dsi probe
 
[  2.133915] [drm:__dw_mipi_dsi_probe] *ERROR* DW: dsi probe ok
 
[  2.139679] [drm:dw_mipi_dsi_stm_probe] *ERROR* DW: stm dsi ok
 
[  2.146438] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  2.153807] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  2.160486] [drm:panel_simple_probe] *ERROR* start to add panel
 
[  2.166493] [drm:panel_simple_probe] *ERROR* panel init done, start to drm add panel
 
[  2.173145] [drm:drm_panel_add] *ERROR* ADD: add pannel to the list
 
[  2.179381] [drm:panel_simple_probe] *ERROR* add to drm panel ok
 
-> NOTE: PANEL ON ROOT NODE ADD
 
 
 
[  2.350320] [drm:ti_sn_bridge_probe] *ERROR* probe bridge
 
[  2.354374] [drm:ti_sn_bridge_probe] *ERROR* check i2c ok, proceed
 
[  2.360719] [drm:ti_sn_bridge_probe] *ERROR* init i2c client ok
 
[  2.366482] [drm:of_drm_find_panel] *ERROR* ADD: loop through list of panel,panel:panel, dev name:panel
 
[  2.375957] [drm:of_drm_find_panel] *ERROR* ADD: panel found
 
[  2.381667] [drm:ti_sn_bridge_probe] *ERROR* find panel or bridge ok
 
[  2.388208] [drm:ti_sn_bridge_probe] *ERROR* enable gpio ok
 
[  2.394020] [drm:ti_sn_bridge_probe] *ERROR* regulator ok
 
[  2.399275] [drm:ti_sn_bridge_probe] *ERROR* parse dsi host ok
 
[  2.406063] [drm:ti_sn_bridge_probe] *ERROR* add bridge
 
-> NOTE: BRIDGE INIT DONE OK
 
[  2.411543] [drm:of_drm_find_panel] *ERROR* ADD: loop through list of panel,panel:panel, dev name:dsi
 
[  2.419787] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  2.425784] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  2.434369] [drm:of_drm_find_panel] *ERROR* ADD: loop through list of panel,panel:panel, dev name:dsi
 
[  2.442311] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  2.448339] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  7.318691] [drm:of_drm_find_panel] *ERROR* ADD: loop through list of panel,panel:panel, dev name:dsi
 
[  7.337999] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  7.342682] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  22.145918] [drm:of_drm_find_panel] *ERROR* ADD: loop through list of panel,panel:panel, dev name:dsi
 
[  22.160483] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  22.165823] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
[  22.535922] [drm:of_drm_find_panel] *ERROR* ADD: loop through list of panel,panel:panel, dev name:dsi
 
[  22.550233] [drm:of_drm_find_panel] *ERROR* ADD: cannot find any
 
[  22.555338] [drm:drm_of_find_panel_or_bridge] *ERROR* DRM no panel found
 
root@myPOD:~#

[LLe.1]

@Erwan SZYMANSKI​ so more detail error here:

drm/drm_of.c

        if (bridge) {
                if (ret) {
 
                        *bridge = of_drm_find_bridge(remote);
                        if (*bridge){
                                ret = 0;
                                DRM_ERROR("DRM bridge found \n");
                        }else
                                DRM_ERROR("DRM get brige error \n"); ---> EXE GOES HERE
                } else {
                        DRM_ERROR("DRM bridge not retrieved because of ret error \n");
                        *bridge = NULL;
                }
 
        }else
                DRM_ERROR("DRM bridge pointer NULL \n");

[LLe.1]

My panel is not exactly like the one mentioned in device tree above, I am using a normal 24 inch LCD monitor with a display port as input. Does it matter? I suppose all simple_panel should work similarly...

[LLe.1]

For the ti-sn65dsi86.c driver, the ti_sn_bridge_probe func finishes successfully but after that no other function is called. I suppose at least ti_sn_bridge_attach or ti_sn_bridge_enable should be called but they are not.

[LLe.1]

I applied this patch to ti-sn65dsi86.c and it helps finding the panel root node but thats all

https://patchwork.kernel.org/project/dri-devel/patch/20191207203553.286017-4-robdclark@gmail.com/