Implementing own DTO to use a 2nd custom CS pin with SPI - output not what I expected

[GoGerriko]

I am using a Linux rockpi-4cplus with 5.15.93-rockchip64 (bullseye).

 

I plan to use SPI1 (GPIO1_A7, GPIO1_B0, GPIO1_B1, GPIO1_B2), and then add in a 2nd device on this SPI bus via a custom CS GPIO pin (GPIO4_D5).

 

I could not find the corresponding script file (.DTS) online (on Github) associated with the object file (rockchip-spi-spidev.dtbo). Please could someone point me to it - I can only find files for "sunxi-DT-overlays".

 

So I decided to create my own DTS file, as follows:

 

/dts-v1/;
/plugin/;

/ {
    fragment@0 {
        target = <&spi1>;

        __overlay__ {
            #address-cells = <1>;
            #size-cells = <0>;
            cs-gpio = <0>, <&gpio4 29 0>;
            status = "okay";

            spidev@0 {
                reg = <0>;
                compatible = "spidev";
                status = "okay";
                spi-max-frequency = <5000000>;
            };            
            
            spidev@1 {
                reg = <1>;
                compatible = "spidev";
                status = "okay";
                spi-max-frequency = <50000000>;
            };
        };
    };
};

 

This compiles and I then added in my own DTBO reference inside armbianEnv.txt (under #overlays=). I also included param_spidev_spi_bus=1, as I discovered this is still needed (where is this check made, btw).

 

When I reboot the following shows up for SPI in the device tree:
 

/proc/device-tree/spi@ff1c0000/status: disabled
/proc/device-tree/spi@ff1d0000/spidev@0/status: okay
/proc/device-tree/spi@ff1d0000/status: okay
/proc/device-tree/spi@ff1d0000/spidev@1/status: okay
/proc/device-tree/spi@ff1e0000/status: disabled
/proc/device-tree/spi@ff1f0000/status: disabled
/proc/device-tree/spi@ff200000/status: disabled

 

So far so good.

 

Interestingly you have to use spidev@0 or spidev@1 in an overlay otherwise it won't compile. So already I am at odds with the current Armbian configuration setup logic (as per overlays readme text for using a different CS and armbian just relies on spidev and not spidev@...).

 

I learnt from another Linux board that I can "bind" the spidev to the correct spi drivers and add in a script (e.g. within rc.local to automate). But first I needed to check what has been setup for the spi drivers. This is where I got a surprise.

 

root@rockpi-4cplus:/boot$ ls -l /sys/bus/spi/devices
total 0
lrwxrwxrwx 1 root root 0 Aug  5  2017 spi0.0 -> ../../../devices/platform/ff1d0000.spi/spi_master/spi0/spi0.0
lrwxrwxrwx 1 root root 0 Aug  5  2017 spi0.1 -> ../../../devices/platform/ff1d0000.spi/spi_master/spi0/spi0.1

 

My SPI1 reference in my device tree overlay (i.e. <&spi1>) was showing up here as spi0.

 

How/ why so??

 

(In my opinion this messes other things up... as shown below when using Python).

 

I assume you have done something similar as per sunxi-DT-overlays where you are using aliases (this really is unnecessary, IMHO)
 

fragment@0 {
  target-path = "/aliases";
  __overlay__ {
    spi0 = "/soc/spi@01c68000";
    spi1 = "/soc/spi@01c69000";
  };
};

 

I then bound these by using the following commands:

 

echo spidev > /sys/bus/spi/devices/spi0.0/driver_override
echo spi0.0 > /sys/bus/spi/drivers/spidev/bind

echo spidev > /sys/bus/spi/devices/spi0.1/driver_override
echo spi0.1 > /sys/bus/spi/drivers/spidev/bind

 

Now after a reboot I get:

 

root@rockpi-4cplus:~$ ls -l /dev/spi*
crw------- 1 root root 153, 0 Apr 15 11:17 /dev/spidev0.0
crw------- 1 root root 153, 1 Apr 15 11:17 /dev/spidev0.1

 

I thought this was good enough.

 

However, when I use Python3 together when SPI pin references it does not like it.

It throws an error "OSError: /dev/spidev1.0 does not exist".

 

Any suggestions.

 

Edited April 15, 2023 by GoGerriko

[going]

@GoGerriko To get started, check out this patch:

patch/kernel/archive/rockchip64-5.15/drv-spi-spidev-remove-warnings.patch

 

And then do it by analogy with sunxi64

Скрытый текст

/dts-v1/;
/plugin/;

/ {
	compatible = "allwinner,sun50i-a64";

	fragment@0 {
		target-path = "/aliases";
		__overlay__ {
			spi0 = "/soc/spi@1c68000";
			spi1 = "/soc/spi@1c69000";
		};
	};

	fragment@1 {
		target = <&spi0>;
		__overlay__ {
			#address-cells = <1>;
			#size-cells = <0>;
			spidev@0 {
				compatible = "armbian,spi-dev";
				status = "disabled";
				reg = <0>;
				spi-max-frequency = <1000000>;
			};
		};
	};

	fragment@2 {
		target = <&spi1>;
		__overlay__ {
			#address-cells = <1>;
			#size-cells = <0>;
			spidev@0 {
				compatible = "armbian,spi-dev";
				status = "disabled";
				reg = <0>;
				spi-max-frequency = <1000000>;
			};
		};
	};
};