[RK3566] Correct DT Overlay for PWM in Radxa 3W

[eshcheglov]

Hello, Mr. Joshua,

I have been trying to understand how the Device Tree Overlay for PWM works on the Radxa 3W board in recent days.

I know it works correctly in the official Radxa distribution called radxa-zero3_debian_bullseye_xfce_b6.img.xz. For this, I simply need to enable the DT Overlay named rk3568-pwm9-m0.dtbo and a directory named pwmchip9 appears in /sys/class/pwm.

I see that in your distribution, all PWM DTO's for the rk3568 chip are disabled (just not present) (I checked here: https://github.com/Joshua-Riek/linux-rockchip/blob/noble/arch/arm64/boot/dts/rockchip/overlay/Makefile).

I have tried the following approaches:

1) I took the official DTS from Radxa, compiled it into .dtbo, and enabled it. As a result, the PWM works, but it has an incorrect name (pwmchip0 instead of pwmchip9). If I enable PWM9 and PWM8 simultaneously, they appear with incorrect names pwmchip0 and pwmchip1, respectively. However, the PWM functions themselves work correctly.

2) I tried taking the .dtbo from the Radxa distribution and connecting it to your distribution. The result is the same.

3) I tried decompiling the DTBO into DTS in the Radxa distribution and then compiling it back from that DTS into DTBO in your distribution. The result is the same.

I also noticed that in all cases, the binary diff does not see any differences between these DTBOs. So, I can assume that the problem lies elsewhere.

I would like to make a merge request to your kernel that adds all PWMs for the Radxa 3W, but until I resolve the issue with incorrect naming, I cannot do so.

Do you have any ideas about what might be causing the incorrect directory naming?

Thank you.

[eshcheglov]

Steps to reproduce:

• Install fresh 24.04 distro

• Check that pwm is emtpy:

  # ls /sys/class/pwm/

• Clone and compile Radxa DT Overlays:

  git clone https://github.com/radxa-pkg/radxa-overlays.git
  cd radxa-overlays
  make build-dtbo -j4

• Install compiled DTBO for PWM9:

cp ./arch/arm64/boot/dts/rockchip/overlays/rk3568-pwm9-m0.dtbo /usr/lib/firmware/6.1.0-1016-rockchip/device-tree/rockchip/overlay/

• Add overlay to U-boot: put line U_BOOT_FDT_OVERLAYS="device-tree/rockchip/overlay/rk3568-pwm9-m0.dtbo" to /etc/default/u-boot then update u-boot:

u-boot-update

Check new config:

$  grep pwm9 /boot/extlinux/extlinux.conf
    fdtoverlays  /lib/firmware/6.1.0-1016-rockchip/device-tree/rockchip/overlay/rk3568-pwm9-m0.dtbo

• Reboot device

• Check again the PWM's:

$ ls /sys/class/pwm/
pwmchip0

directory is named pwmchip0, but it must be named pwmchip9

$ uname -a
Linux ubuntu 6.1.0-1016-rockchip #16-Ubuntu SMP Thu Jun  6 00:11:54 UTC 2024 aarch64 aarch64 aarch64 GNU/Linux

[RadxaStephen]

I think the aliases name is needed in device tree. Like this. https://github.com/radxa/kernel/blob/linux-5.10-gen-rkr4.1/arch/arm64/boot/dts/rockchip/rk3568.dtsi#L57

[eshcheglov]

I think the aliases name is needed in device tree. Like this. https://github.com/radxa/kernel/blob/linux-5.10-gen-rkr4.1/arch/arm64/boot/dts/rockchip/rk3568.dtsi#L57

The corresponding file in the linux-rockchip kernel by Joshua looks pretty limited (I'd rather say "cut down"). I think it was done for some reasons. Maybe because of the lack of QA possibilities for Radxa Rock3 boards?..

Okay, I'll test it, thanks!

[eshcheglov]

No result still.

Tried this:

git clone --depth 1 https://github.com/Joshua-Riek/linux-rockchip.git
cd linux-rockchip/arch/arm64/boot/dts/rockchip
vim rk356x.dtsi  

Lines added to aliases section:

<...>
                spi3 = &spi3;
                pwm0 = &pwm0;
                pwm1 = &pwm1;
                pwm2 = &pwm2;
                pwm3 = &pwm3;
                pwm4 = &pwm4;
                pwm5 = &pwm5;
                pwm6 = &pwm6;
                pwm7 = &pwm7;
                pwm8 = &pwm8;
                pwm9 = &pwm9;
                pwm10 = &pwm10;
                pwm11 = &pwm11;
                pwm12 = &pwm12;
                pwm13 = &pwm13;
                pwm14 = &pwm14;
                pwm15 = &pwm15;
        };
<...>

cpp -I ~/linux-rockchip/include/ -nostdinc -undef -x assembler-with-cpp rk3566-radxa-zero3.dts rk3566-radxa-zero3.dts.preprocessed
dtc -@ -I dts rk3566-radxa-zero3.dts.preprocessed -O dtb -o /tmp/rockchip.dtb
cp /tmp/rockchip.dtb /usr/lib/firmware/6.1.0-1016-rockchip/device-tree/rockchip/rk3566-radxa-zero3.dtb
reboot

I saw my changes in the rk3566-radxa-zero3.dts.preprocessed file, so I assume that I changed the correct line in the correct file