AM335x Beaglebone Black LCD doesn't work

Hi Yordan,

I modified the .dtb file like the am335x-evm. I copied the setting of the LCD pins and the backlight, but the LCD doesn't work.  I attached the .dtb file. I modified the symlink (I attached the contenent of the boot folder):

matteo@matteo-Compaq-Presario-CQ61-Notebook-PC:~/Sitara/targetNFS/boot$ ll
totale 3424
drwxr-xr-x  3 root root    4096 dic  6 21:12 ./
drwxr-xr-x 21 root root    4096 ott  4 01:59 ../
lrwxrwxrwx  1 root root      24 dic  6 11:15 am335x-boneblack.dtb -> am335x-boneblack-LCD.dtb
-rw-rw-r--  1 root root   37521 dic  6 20:52 am335x-boneblack-LCD.dtb
drwxr-xr-x  2 root root    4096 dic  6 21:12 old files/
lrwxrwxrwx  1 root root      25 ott  4 01:59 zImage -> zImage-4.4.19-gdb0b54cdad
-rw-r--r--  1 root root 3451352 ott  3 23:53 zImage-4.4.19-gdb0b54cdad
matteo@matteo-Compaq-Presario-CQ61-Notebook-PC:~/Sitara/targetNFS/boot$

the boot seems to be ok:

TFTP from server 192.168.1.101; our IP address is 192.168.1.100                 
Filename 'zImage-am335x-evm.bin'.                                               
Load address: 0x82000000                                                        
Loading: #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #################################################################      
         #########################                                              
         1.4 MiB/s                                                              
done                                                                            
Bytes transferred = 3451352 (34a9d8 hex)                                        
link up on port 0, speed 100, full duplex                                       
Using ethernet@4a100000 device                                                  
TFTP from server 192.168.1.101; our IP address is 192.168.1.100                 
Filename 'am335x-boneblack.dtb'.                                                
Load address: 0x88000000                                                        
Loading: ########                                                               
         1.2 MiB/s                                                              
done                                                                            
Bytes transferred = 37004 (908c hex)                                            
Kernel image @ 0x82000000 [ 0x000000 - 0x34a9d8 ]                               
## Flattened Device Tree blob at 88000000                                       
   Booting using the fdt blob at 0x88000000                                     
   Loading Device Tree to 8fff3000, end 8ffff08b ... OK                         
                                                                                
Starting kernel ... 

but the result is always the same. Could you help me again, please?

Matteo

/*
 * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
/dts-v1/;

#include "am33xx.dtsi"
#include "am335x-bone-common.dtsi"
#include <dt-bindings/pwm/pwm.h>
/*#include <dt-bindings/display/tda998x.h>*/

/ {
    model = "TI AM335x BeagleBone Black";
    compatible = "ti,am335x-bone-black", "ti,am335x-bone", "ti,am33xx";

    backlight {
        compatible = "pwm-backlight";
        pwms = <&ecap0 0 50000 0>;
        brightness-levels = <0 51 53 56 62 75 101 152 255>;
        default-brightness-level = <8>;
    };


    panel {
        compatible = "ti,tilcdc,panel";
        status = "okay";
        pinctrl-names = "default";
        pinctrl-0 = <&lcd_pins_s0>;
        panel-info {
            ac-bias           = <255>;
            ac-bias-intrpt    = <0>;
            dma-burst-sz      = <16>;
            bpp               = <32>;
            fdd               = <0x80>;
            sync-edge         = <0>;
            sync-ctrl         = <1>;
            raster-order      = <0>;
            fifo-th           = <0>;
        };

        display-timings {
            800x480p62 {
                clock-frequency = <30000000>;
                hactive = <800>;
                vactive = <480>;
                hfront-porch = <39>;
                hback-porch = <39>;
                hsync-len = <47>;
                vback-porch = <29>;
                vfront-porch = <13>;
                vsync-len = <2>;
                hsync-active = <1>;
                vsync-active = <1>;
            };
        };
    };

};

&ldo3_reg {
    regulator-min-microvolt = <1800000>;
    regulator-max-microvolt = <1800000>;
    regulator-always-on;
};

&mmc1 {
    vmmc-supply = <&vmmcsd_fixed>;
};

&mmc2 {
    vmmc-supply = <&vmmcsd_fixed>;
    pinctrl-names = "default";
    pinctrl-0 = <&emmc_pins>;
    bus-width = <8>;
    status = "okay";
};

&cpu0_opp_table {
    /*
     * All PG 2.0 silicon may not support 1GHz but some of the early
     * BeagleBone Blacks have PG 2.0 silicon which is guaranteed
     * to support 1GHz OPP so enable it for PG 2.0 on this board.
     */
    oppnitro@1000000000 {
        opp-supported-hw = <0x06 0x0100>;
    };
};


&am33xx_pinmux {
    lcd_pins_s0: lcd_pins_s0 {
        pinctrl-single,pins = <
            0x20 (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad8.lcd_data23 */
            0x24 (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad9.lcd_data22 */
            0x28 (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad10.lcd_data21 */
            0x2c (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad11.lcd_data20 */
            0x30 (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad12.lcd_data19 */
            0x34 (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad13.lcd_data18 */
            0x38 (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad14.lcd_data17 */
            0x3c (PIN_OUTPUT | MUX_MODE1)        /* gpmc_ad15.lcd_data16 */
            0xa0 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data0.lcd_data0 */
            0xa4 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data1.lcd_data1 */
            0xa8 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data2.lcd_data2 */
            0xac (PIN_OUTPUT | MUX_MODE0)        /* lcd_data3.lcd_data3 */
            0xb0 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data4.lcd_data4 */
            0xb4 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data5.lcd_data5 */
            0xb8 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data6.lcd_data6 */
            0xbc (PIN_OUTPUT | MUX_MODE0)        /* lcd_data7.lcd_data7 */
            0xc0 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data8.lcd_data8 */
            0xc4 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data9.lcd_data9 */
            0xc8 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data10.lcd_data10 */
            0xcc (PIN_OUTPUT | MUX_MODE0)        /* lcd_data11.lcd_data11 */
            0xd0 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data12.lcd_data12 */
            0xd4 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data13.lcd_data13 */
            0xd8 (PIN_OUTPUT | MUX_MODE0)        /* lcd_data14.lcd_data14 */
            0xdc (PIN_OUTPUT | MUX_MODE0)        /* lcd_data15.lcd_data15 */
            0xe0 (PIN_OUTPUT | MUX_MODE0)        /* lcd_vsync.lcd_vsync */
            0xe4 (PIN_OUTPUT | MUX_MODE0)        /* lcd_hsync.lcd_hsync */
            0xe8 (PIN_OUTPUT | MUX_MODE0)        /* lcd_pclk.lcd_pclk */
            0xec (PIN_OUTPUT | MUX_MODE0)        /* lcd_ac_bias_en.lcd_ac_bias_en */
        >;
    };
    
    ecap0_pins: backlight_pins {
        pinctrl-single,pins = <
            0x164 0x0    /* eCAP0_in_PWM0_out.eCAP0_in_PWM0_out MODE0 */
        >;
    };

    mcasp0_pins: mcasp0_pins {
        pinctrl-single,pins = <
            AM33XX_IOPAD(0x9ac, PIN_INPUT_PULLUP | MUX_MODE0) /* mcasp0_ahcklx.mcasp0_ahclkx */
            AM33XX_IOPAD(0x99c, PIN_OUTPUT_PULLDOWN | MUX_MODE2) /* mcasp0_ahclkr.mcasp0_axr2*/
            AM33XX_IOPAD(0x994, PIN_OUTPUT_PULLUP | MUX_MODE0) /* mcasp0_fsx.mcasp0_fsx */
            AM33XX_IOPAD(0x990, PIN_OUTPUT_PULLDOWN | MUX_MODE0) /* mcasp0_aclkx.mcasp0_aclkx */
            AM33XX_IOPAD(0x86c, PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* gpmc_a11.GPIO1_27 */
        >;
    };
};

&lcdc {
      status = "okay";
};

&epwmss0 {
    status = "okay";

    ecap0: ecap@48300100 {
        status = "okay";
        pinctrl-names = "default";
        pinctrl-0 = <&ecap0_pins>;
    };
};

&rtc {
    system-power-controller;
};

&mcasp0    {
    #sound-dai-cells = <0>;
    pinctrl-names = "default";
    pinctrl-0 = <&mcasp0_pins>;
    status = "okay";
    op-mode = <0>;    /* MCASP_IIS_MODE */
    tdm-slots = <2>;
    serial-dir = <    /* 0: INACTIVE, 1: TX, 2: RX */
            0 0 1 0
        >;
    tx-num-evt = <32>;
    rx-num-evt = <32>;
};

&sgx {
    status = "okay";
};

/ {
    clk_mcasp0_fixed: clk_mcasp0_fixed {
        #clock-cells = <0>;
        compatible = "fixed-clock";
        clock-frequency = <24576000>;
    };

    clk_mcasp0: clk_mcasp0 {
        #clock-cells = <0>;
        compatible = "gpio-gate-clock";
        clocks = <&clk_mcasp0_fixed>;
        enable-gpios = <&gpio1 27 0>; /* BeagleBone Black Clk enable on GPIO1_27 */
    };

    sound {
        compatible = "simple-audio-card";
        simple-audio-card,name = "TI BeagleBone Black";
        simple-audio-card,format = "i2s";
        simple-audio-card,bitclock-master = <&dailink0_master>;
        simple-audio-card,frame-master = <&dailink0_master>;

        dailink0_master: simple-audio-card,cpu {
            sound-dai = <&mcasp0>;
            clocks = <&clk_mcasp0>;
        };

    };
};

Hi Yordan,

I'm a little bit confuse. Does the .dts file work with the "overlay" mentality? This means that the sets after the #include overlay the previous sets, is correct?

I checked the schematics of the BBB and I see that the TDA19988 converts the LCD pins signals to HDMI. This means that the LCD signals are already available, because the HDMI works, is correct?

The I2C0 bus is necessary only for the audio, is not important when the LCD is connected.

Instead the backlight is different. Is a signal that doesn't share nothing with the audio/video signals. During my tests the display is always deep black. Without the backlight nothing is visible in the LCD pannel so is not possible to understand if the LDC signals are ok or not ok. I fear that the backlight signal is not set correctly (and I haven't a scope that confirm this theory).

My question is simple: I'm using a standard 4DCAPE-70T display: does exist a .dts file for this display?

Thanks