SN65DSI84: Unable to detect SN65DSI84 on i2c

Hello Team, 

Please find the DTSI entry  we did for bridge chip and LVDS Panel

&i2c2 {
        #address-cells = <1>;
        #size-cells = <0>;
        pinctrl-names = "default";
        pinctrl-0 = <&i2c2_pins>;
        clock-frequency = <400000>;
        status="okay";
	dsi_lvds_bridge: sn65dsi84@2d {
                    compatible = "ti,sn65dsi84";
                    reg = <0x2d>;
                    ti,data-lanes = <4>;
                    ti,lvds-format = <0>;
                    ti,lvds-bpp = <24>;
                    ti,width-mm = <217>;
                    ti,height-mm = <136>;
                    ti,lvds-channels = <1>;
                    enable-gpios = <&exp1 10 GPIO_ACTIVE_HIGH>;
                    status = "okay";
                    timings_1024x600_60:display-timings {
                            lvds {
                                    clock-frequency = <65000000>;
                                    hactive = <1280>;
                                    vactive = <800>;
                                    hback-porch = <48>;
                                    hfront-porch = <48>;
                                    vback-porch = <10>;
                                    vfront-porch = <10>;
                                    hsync-len = <64>;
                                    vsync-len = <4>;
                                    hsync-active = <0>;
                                    vsync-active = <0>;
                                    de-active = <1>;
                                    pixelclk-active = <0>;
                            };
                    };
                    ports{
                            #address-cells = <1>;
                            #size-cells = <0>;
                            port@0 {
                                    reg = <0>;
                                    bridge_in: endpoint {
                                            remote-endpoint = <&dsi0_out>;
                                    };
                            };
                            port@2 {
                                    reg = <2>;
                                    bridge_out: endpoint {
                                            remote-endpoint = <&lvds_in>;
                                    };
                            };
                    };
    	};
};

&dsi0 {
        status = "okay";
        #address-cells = <1>;
        #size-cells = <0>;

        ports {
                #address-cells = <1>;
                #size-cells = <0>;

                port@1 {
                        dsi0_out: endpoint {
                                remote-endpoint = <&bridge_in>;
                                data-lanes = <1 2 3 4>;
                        };
                };
        };
};


lvds_panel: lvds {
                compatible = "panel-lvds";
                label = "AMA-101A01-DU2511-G020";
                width-mm = <217>;
                height-mm = <136>;
                data-mapping = "vesa-24";
                backlight = <&backlight>;
                status = "okay";

                panel-timing {
                    clock-frequency = <75000000>;
                    hactive = <1280>;
                    vactive = <800>;
                    hback-porch = <48>;
                    hfront-porch = <48>;
                    vback-porch = <10>;
                    vfront-porch = <10>;
                    hsync-len = <64>;
                    vsync-len = <4>;
                    hsync-active = <0>;
                    vsync-active = <0>;
                    de-active = <1>;
                    pixelclk-active = <0>;
                };

                ports {
                        port@0 {
                                lvds_in: endpoint {
                                        remote-endpoint = <&bridge_out>;
                                };
                        };
                };
        };



backlight: pwm-backlight {
                compatible = "pwm-backlight";
                pwms = <&mtu3 0 500000>;
                brightness-levels = <100 99 98 97 96 95 94 93 92 91
                        90 89 88 87 86 85 84 83 82 81
                        80 79 78 77 76 75 74 73 72 71
                        70 69 68 67 66 65 64 63 62 61
                        60 59 58 57 56 55 54 53 52 51
                        50 49 48 47 46 45 44 43 42 41
                        40 39 38 37 36 35 34 33 32 31
                        30 29 28 27 26 25 24 23 22 21
                        20 19 18 17 16 15 14 13 12 11
                        10  9  8  7  6  5  4  3  2  1
                         0>;
                default-brightness-level = <50>;
                status = "okay";
        };

Hello Vishesh,

Is this initialization sequence needed for I2C detection of the bridge chip IC. As we are not able to detect this IC.

In the datasheet it is mentioned that "The SN65DSI84 local I2C interface is enabled when EN is input high" , so this means for normal I2C detection we need only EN pin to be high not full initialization sequence needs to be followed. Please correct us if our understanding is wrong. 

Hey Nilesh,

You are correct that the I2C should be enabled simply based of the EN, but its best to remove all causes of error when debugging. Ensuring the initialization process is correct will make sure that any issue is not stemming from there.

Also have you tried writing and reading from address 0x2C as a I mentioned?

Are you able to send the actual register values being written to? it will be mush easier for me to confirm that you are properly setting registers using that. 

Hello Vishesh,

Can you provide reference device tree entry for SN65DSI84 Bridge chip? And also can you let us know if attached DTSI entry provided above is correct or not.

Hey Nilesh,

I cannot verify the DTSI entry without verifying with the panel specs you are using. Regarding the reference tree entry, TI does not use this. We use an aardvark I2C adapter, but given that you cannot read or write to the device I cannot support. Can you confirm you are writing to the correct address based of the ADDR pin on the device?

Hi Vishesh,

We are able to get the bridge chip detected in uboot by only enabling the EN pin. And we checked the signals by probing the i2c line in both kernel and uboot, we get proper address of bridge chip IC in uboot, but in kernel the address is not appropriate.
And can you provide any reference of DTSI node which you use for in your source.

Thanks
Nilesh