PROCESSOR-SDK-AM62X: LVDS not working...

Hello Maulik,

Our recommendation is to keep the LCD dtbo as the TI EVM and change the timing parameter based on the bridge requirements: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/gpu/drm/panel/panel-simple.c?h=ti-linux-5.10.y#n2821 

Here is the section that you would need to change:

	.clock = 150275,
	.hdisplay = 1920,
	.hsync_start = 1920 + 32,
	.hsync_end = 1920 + 32 + 52,
	.htotal = 1920 + 32 + 52 + 24,
	.vdisplay = 1200,
	.vsync_start = 1200 + 24,
	.vsync_end = 1200 + 24 + 8,
	.vtotal = 1200 + 24 + 8 + 3,


Regards,

Krunal

Hi Krunal,

Thanks for response. 

As I mentioned in my earlier post that we are using OLDI interface of DSS for the LVDS display. And Please note that We are not using RGB interface of DSS (eg. VOUT* Hsync, VSync, etc pins) but in place of RGB pins we are using alternate functions other than display.

Test 1) TI EVM DTBO file

I tried to use EVM dtbo - k3-am625-sk-oldi-panel.dtbo but I am facing some issue while booting the kernel. Here below I have attached error logs for reference. I verified that dtbo file is present in card.

=> setenv name_overlays k3-am625-sk-oldi-panel.dtbo

=> saveenv

Saving Environment to MMC... Writing to MMC(0)... MMC: block number 0x3500 exceeds max(0x2000)

failed

Failed (1)

=> boot

switch to partitions #0, OK

mmc1 is current device

SD/MMC found on device 1

Failed to load 'boot.scr'

1830 bytes read in 3 ms (595.7 KiB/s)

Loaded env from uEnv.txt

Importing environment from mmc1 ...

Running uenvcmd ...

1 bytes read in 2 ms (0 Bytes/s)

Already setup.

21256704 bytes read in 884 ms (22.9 MiB/s)

62482 bytes read in 6 ms (9.9 MiB/s)

1330 bytes read in 4 ms (324.2 KiB/s)

failed on fdt_overlay_apply(): FDT_ERR_NOTFOUND

979 bytes read in 3 ms (318.4 KiB/s)

failed on fdt_overlay_apply(): FDT_ERR_BADMAGIC

base fdt does did not have a /__symbols__ node

make sure you've compiled with -@

2478 bytes read in 3 ms (806.6 KiB/s)

failed on fdt_overlay_apply(): FDT_ERR_BADMAGIC

base fdt does did not have a /__symbols__ node

make sure you've compiled with -@

ERROR: Did not find a cmdline Flattened Device Tree

Could not find a valid device tree

Test 2)As We were not successful for the LVDS to HDMI testing, So We tried to test single link 18bit LVDS display directly over the dual link OLDI interface of the CPU. We have  AMA-070A04-DU2511-G010 display with us.

We modified display node as per our LVDS  panel and currently using panel-simple driver for the same. Here below I attached device tree changes of our custom board based on am6254 processor for your reference purpose.

We also tested single link lvds using below code but we did't get any signal over oscilloscope regarding LVDS interface from CPU.

/ {
...

        display0 {
                compatible = "rocktech,rk101ii01d-ct";
                backlight = <&lcd_bl>;
                pinctrl-names = "default";
                pinctrl-0 = <&lvds_enable_pin>;

                port {
                        lcd_in0: endpoint {
                                remote-endpoint = <&oldi_out0>;
                        };
                };
        };
...
};

&dss {
        status = "okay";
};

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

        port@0 {
                reg = <0>;

                oldi_out0: endpoint {
                        remote-endpoint = <&lcd_in0>;
                };
        };
};

Then, We tried dual link lvds same like TI EVM but result is still the same as single link. Here below I attached device tree changes. We also did not get /dev/fb0 node for display.

      
	  panel {
                label = "AMA-070A04-DU2511-G010";
                status="okay";
                compatible = "panel-simple";
							data-mapping="jeida-18";
                panel-timing {
                        clock-frequency = <25000000>;
                        hactive = <800>;
                        vactive = <480>;
                        hfront-porch = <8>;
                        hback-porch = <8>;
                        vback-porch = <8>;
                        vfront-porch = <8>;
                        hsync-len = <8>;
                        vsync-len = <4>;
                        hsync-active = <0>;
                        vsync-active = <0>;
                        de-active = <1>;
                        pixelclk-active = <0>;
                };

                port@0 {
                       dual-lvds-odd-pixels;
                       lcd_in0: endpoint {
                               remote-endpoint = <&oldi_out0>;
                       };
                };

                port@1 {
                       dual-lvds-even-pixels;
                       lcd_in1: endpoint {
                                remote-endpoint = <&oldi_out1>;
                       };
                };
        };





&dss {
        status = "okay";
	pinctrl-names = "default";
        pinctrl-0 = <&main_oldi0_pins_default>;
};

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

	port@0 {
		reg = <0>;
		oldi_out0: endpoint {
			remote-endpoint = <&lcd_in0>;
		};
	};

	port@2 {
		reg = <2>;
		oldi_out1: endpoint {
			remote-endpoint = <&lcd_in1>;
		};
	};

};

We would like to know why LVDS signals are not generated from CPU? 

Thanks,

Maulik

Thank you Krunal for the answer.