Custom DTBO for SPI LCD (BBGW)

[serpent213]

Environment

• Elixir version (elixir -v):

Erlang/OTP 25 [erts-13.2.2.1] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]
                                            
Elixir 1.14.5 (compiled with Erlang/OTP 25)

• Nerves environment: (mix nerves.env --info)

==> nerves                                                                                                                                                                        
==> nerves_bbgw                                                                                                                                                                   
|nerves_bootstrap| Environment Package List                                                                                                                                       
                                                                                                                                                                                  
  Pkg:         bbgw_spi                                                                                                                                                           
  Vsn:         2.17.2                                                                                                                                                             
  Type:        system                                                                                                                                                             
  BuildRunner: {Nerves.Artifact.BuildRunners.Local, [make_args: ["source", "all", "legal-info"]]}                                                                                 
                                                                                                                                                                                  
  Pkg:         nerves_system_br                                                                                                                                                   
  Vsn:         1.22.5                                                                                                                                                             
  Type:        system_platform                                                                                                                                                    
  BuildRunner: {nil, []}                                                                                                                                                          

  Pkg:         nerves_toolchain_armv7_nerves_linux_gnueabihf
  Vsn:         1.8.0
  Type:        toolchain
  BuildRunner: {Nerves.Artifact.BuildRunners.Local, []}

  Pkg:         nerves_toolchain_ctng
  Vsn:         1.9.3
  Type:        toolchain_platform
  BuildRunner: {nil, []}

|nerves_bootstrap| Loadpaths Start

|nerves_bootstrap| Precompile Start

==> nerves_toolchain_armv7_nerves_linux_gnueabihf
|nerves_bootstrap| Compile.NervesPackage start

|nerves_bootstrap| Compile.NervesPackage end 

==> bbgw_spi
Generated bbgw_spi app
|nerves_bootstrap| Compile.NervesPackage start

|nerves_bootstrap| Compile.NervesPackage end 

==> nerves_bbgw
|nerves_bootstrap| Precompile End


Nerves environment
  MIX_TARGET:   bbgw_spi
  MIX_ENV:      dev

|nerves_bootstrap| Environment Variable List
  target:     bbgw_spi
  toolchain:  /home/serpent/.nerves/artifacts/nerves_toolchain_armv7_nerves_linux_gnueabihf-linux_x86_64-1.8.0
  system:     /home/serpent/.nerves/artifacts/bbgw_spi-portable-2.17.2
  app:        .

|nerves_bootstrap| Loadpaths End

• Boot log with additional overlay:

U-Boot 2021.10 (Apr 04 2023 - 02:26:05 +0000)

CPU  : AM335X-GP rev 2.1
Model: TI AM335x BeagleBone Black
DRAM:  512 MiB
Reset Source: Global warm SW reset has occurred.
Reset Source: Power-on reset has occurred.
RTC 32KCLK Source: External.
WDT:   Started with servicing (60s timeout)
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
Loading Environment from MMC... OK
Board: BeagleBone Black
BeagleBone Black:
Model: SeeedStudio BeagleBone Green Wireless:
BeagleBone Cape EEPROM: no EEPROM at address: 0x54
BeagleBone Cape EEPROM: no EEPROM at address: 0x55
BeagleBone Cape EEPROM: no EEPROM at address: 0x56
BeagleBone Cape EEPROM: no EEPROM at address: 0x57
Net:   Could not get PHY for ethernet@4a100000: addr 0
eth2: ethernet@4a100000
board_name=[A335BNLT] ...
board_rev=[GW1A] ...
loading /zImage.a ...
2860152 bytes read in 253 ms (10.8 MiB/s)
uboot_overlays: [uboot_base_dtb=am335x-bonegreen-wireless-uboot-univ.dtb] ...
uboot_overlays: Switching too: dtb=am335x-bonegreen-wireless-uboot-univ.dtb ...
loading /boot/am335x-bonegreen-wireless-uboot-univ.dtb ...
207617 bytes read in 35 ms (5.7 MiB/s)
uboot_overlays: [fdt_buffer=0x60000] ...
uboot_overlays: loading /lib/firmware/spi0_ili9341_display.dtbo ...
2417 bytes read in 109 ms (21.5 KiB/s)
uboot_overlays: loading /lib/firmware/BB-BONE-eMMC1-01-00A0.dtbo ...
1614 bytes read in 47 ms (33.2 KiB/s)
uboot_overlays: loading /lib/firmware/BB-BBGW-WL1835-00A0.dtbo ...
4289 bytes read in 38 ms (109.4 KiB/s)
debug: [console=ttyS0,115200n8 coherent_pool=1M bone_capemgr.uboot_capemgr_enabled=1 root=/dev/mmcblk0p2 rootfstype=squashfs rootwait coherent_pool=1M net.ifnames=0 omap_wdt.early_enable=1 omap_wdt.timer_margin=120 quiet] ...
debug: [bootz 0x82000000 - 88000000] ...
Kernel image @ 0x82000000 [ 0x000000 - 0x2ba478 ]
## Flattened Device Tree blob at 88000000
   Booting using the fdt blob at 0x88000000
   Loading Device Tree to 8ff69000, end 8fffffff ... OK

Starting kernel ...

[    0.159780] l3-aon-clkctrl:0000:0: failed to disable
[    6.058566] gpio-of-helper ocp:cape-universal: Failed to get gpio property of 'P8_03'
[    6.058589] gpio-of-helper ocp:cape-universal: Failed to create gpio entry
[    6.069856] wkup_m3_ipc 44e11324.wkup_m3_ipc: could not get rproc handle
[    6.378639] pinctrl-single 44e10800.pinmux: pin PIN30 already requested by 481a6000.serial; cannot claim for leds
[    6.389311] pinctrl-single 44e10800.pinmux: pin-30 (leds) status -22
[    6.395742] pinctrl-single 44e10800.pinmux: could not request pin 30 (PIN30) from group pinmux_bt_pins  on device pinctrl-single
[    6.407370] leds-gpio leds: Error applying setting, reverse things back
[    6.424305] omap_voltage_late_init: Voltage driver support not added
Erlang/OTP 25 [erts-13.2] [source] [32-bit] [smp:1:1] [ds:1:1:10] [async-threads:1]

pinctrl errors are exactly the same without overlay. System config is unchanged except for additional BR packages.

Changes in provisioning.conf:

uboot_setenv(uboot-env, "uboot_overlay_addr4", "/lib/firmware/spi0_ili9341_display.dtbo")
#uboot_setenv(uboot-env, "enable_uboot_cape_universal", "1")

Actual U-Boot env on target:

iex(1)> ubootenv(~r/^uboot_/)                                                                  
uboot_base_dtb="am335x-boneblack-uboot.dtb"
uboot_base_dtb_univ="am335x-bonegreen-wireless-uboot-univ.dtb"
uboot_emmc="BB-BONE-eMMC1-01-00A0.dtbo"
uboot_overlay_addr4="/lib/firmware/spi0_ili9341_display.dtbo"
uboot_wireless="BB-BBGW-WL1835-00A0.dtbo"
:ok
iex(2)> ubootenv(~r/^enable_/) 
enable_uboot_overlays="1"
:ok

DTS file package/extra-dts/spi0_ili9341_display.dts:

// run `make extra-dts-rebuild` in Nerves shell to rebuild manually, then `make all` to bundle

/dts-v1/;
/plugin/;

#include <dt-bindings/pinctrl/omap.h>

/ {
  fragment@1 {
    target-path="/";
    __overlay__ {
      compatible = "ti,am335x-bone-green-wireless", "ti,am335x-bone-green", "ti,am335x-bone", "ti,am33xx";

      // /* state the resources this cape uses */
      // exclusive-use =
      //   /* the pin header uses */
      //   /* "P9.17",	/* spi0_cs0 */
      //   "P9.18",	/* spi0_d1 */
      //   "P9.21",	/* spi0_d0 */
      //   "P9.22",	/* spi0_sclk */
      //   "P9.16",  /* backlight LED */
      //   "P9.24",  /* SPI DC (direction) */
      //   "P9.23",  /* reset */
      //   /* the hardware ip uses */
      //   "spi0",
      //   "ehrpwm1B";
    };
  };

  /*
  * Free up the pins used by the cape from the pinmux helpers.
  */
  fragment@2 {
    target = <&ocp>;
    __overlay__ {
      P9_18_pinmux { status = "disabled"; };
      P9_21_pinmux { status = "disabled"; };
      P9_22_pinmux { status = "disabled"; };
      P9_16_pinmux { status = "disabled"; };
      P9_24_pinmux { status = "disabled"; };
      P9_23_pinmux { status = "disabled"; };
    };
  };

  fragment@3 {
    target = <&am33xx_pinmux>;

    __overlay__ {
      backlight_pins_default: backlight_pins_default {
        // P9.16
        pinctrl-single,pins = <
          AM33XX_IOPAD(0x84c, PIN_OUTPUT | MUX_MODE6) /* (T14) gpmc_a3.ehrpwm1B */
        >;
      };

      spi_dc_pins_default: spi_dc_pins_default {
        // P9.24
        pinctrl-single,pins = <
          AM33XX_IOPAD(0x984, PIN_OUTPUT | MUX_MODE7) /* (D15) uart1_txd.gpio0[15] */
        >;
      };

      reset_pins_default: reset_pins_default {
        // P9.23
        pinctrl-single,pins = <
          AM33XX_IOPAD(0x844, PIN_OUTPUT | MUX_MODE7) /* (V14) gpmc_a1.gpio1[17] */
        >;
      };

      spi0_pins_default: spi0_pins_default {
        // P9.22, P9.21, P9.18
        pinctrl-single,pins = <
          AM33XX_IOPAD(0x950, PIN_OUTPUT | MUX_MODE0) /* (A17) spi0_sclk.spi0_sclk */
          AM33XX_IOPAD(0x954, PIN_INPUT | MUX_MODE0) /* (B17) spi0_d0.spi0_d0 */
          AM33XX_IOPAD(0x958, PIN_OUTPUT | MUX_MODE0) /* (B16) spi0_d1.spi0_d1 */
        >;
      };
    };
  };

  fragment@4 {
    target = <&epwmss2>;
    __overlay__ {
      status = "okay";
    };
  };

  fragment@5 {
    target = <&ehrpwm2>;
    __overlay__ {
      status = "okay";
    };
  };

  fragment@6 {
    target = <&ocp>;
    __overlay__ {
      backlight {
        compatible = "pwm-backlight";
        pinctrl-names	= "default";
        pinctrl-0	= <&backlight_pins_default>;
        pwms = <&ehrpwm1 1 500000>;

        brightness-levels = <0 4 8 16 32 64 128 255>;
        default-brightness-level = <6>;
      };
    };
  };

  fragment@7 {
    target = <&spi0>;
    __overlay__ {
      // avoid warning
      #address-cells = <1>;
      #size-cells = <0>;

      status		= "okay";
      pinctrl-names	= "default";
      pinctrl-0	= <&spi0_pins_default>;

      ti,spi-num-cs = <0>;

      /*
      lcd@0 {
        compatible = "ilitek,ili9341";
        reg = <0>;
        buswidth = <8>;
        spi-max-frequency = <24000000>;
        dc-gpios = <&gpio0 15 0>;     // P9_24
        reset-gpios = <&gpio1 17 0>;  // P9_23
        rotation = <270>;
        backlight = <&backlight>;
        status = "okay";
      };
      */
    };
  };
};

Current behavior

• Universal cape seems always to be loaded
  Even changing uboot_base_dtb and uboot_base_dtb_univ to am335x-bonegreen-wireless.dtb does not make any difference.
• /sys/class/backlight does not show up
• DTBO becomes unloadable when enabling the lcd part

Expected behavior

PWM backlight should be available.

I'm fairly new to the whole device tree business, so probably I made some mistakes in my DTS.

Where can I find information about exclusive-use? Is it BeagleBone specific? Some overlays make use of it, others disable the pinmux nodes (like I did for now).

Is <&ehrpwm1 1 x> the right way to address ehrpwm1B? Where can I find this kind of information?

Any pointers appreciated to get this to work.