How to enable SPI and I2C on radxa Rock 4?

[AMuellerAtAHS]

Currently I can't find any explanation, how to use i2c and spi on radxa Rock 4 (SE)? I found some discussions where overlays are used inside /boot/armbianEnv.txt, but I can't find that file. Instead there exists /boot/dietpiEnv.txt. Is it the same?
Where can I find informations about the parameters? And do I need any extra steps in /boot/dietpi.txt or something else?

[MichaIng]

I2C should be enabled by default. For SPI, try adding spi-spidev to the overlays= line in /boot/dietpiEnv.txt. Have a look at available overlays in /boot/dtb/rockchip/overlay. Those can be generally added, using the filename minus prefix and ending. But not all of them are compatible with the ROCK 4/RK3399 and even not all of those do actually work: #4596

[MichaIng]

So the file is present when you do apply the i2c7 overlay and it is missing when you remove it, right? Then all works as expected, that node is disabled by default and the overlay does nothing more than enabling it, so it seems to use 400,000 Hz by default: https://github.com/armbian/build/blob/main/patch/kernel/archive/rockchip64-5.15/general-rockchip-overlays.patch#L225-L241

Or did you do something else than adding i2c7 to /boot/dietpiEnv.txt?

[AMuellerAtAHS]

Hmm no. Let me try to explain.
I already decompiled and changed the original rockchip-i2c7.dtbo and added the clock-frequency parameter.

# dtc -I dtb -O dts /boot/dtb-5.15.93-rockchip64/rockchip/overlay/rockchip-i2c7.dtbo -o rockchip-i2c7-400k.dts
# nano rockchip-i2c7-400k.dts

/dts-v1/;

/ {
        compatible = "rockchip,rk3399";

        fragment@0 {
                target-path = "/i2c@ff160000";

                __overlay__ {
                        status = "okay";
                        /* Added this clock-frequency parameter */
                        clock-frequency = <400000>;
                };
        };
};

# armbian-add-overlay rockchip-i2c7-400k.dts 

With that user-overlay I get the following:

# od -bc /proc/device-tree/i2c@ff160000/clock-frequency

0000000 000 006 032 200
         \0 006 032 200
0000004

But with the original rockchip-i2c7.dtbo I get:

# od -bc /proc/device-tree/i2c@ff160000/clock-frequency
od: /proc/device-tree/i2c@ff160000/clock-frequency: File or directory not found

If the original overlay doesn't have any clock-frequency set. Am I able to set one which is used by the driver?

How can I test the functionality?

I tried with:

# i2cdetect -y 7 
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

[MichaIng]

Ah okay, so then it is the same as with my NanoPi R4S, which also does not have the clock-frequency at this node. I've no idea why and I don't know whether just adding it is actually effective. I suggest you just test it with the MCP2515? I'm also not sure how to test the I2C frequency or do some sorts of dry run from the I2C host itself.

[AMuellerAtAHS]

Hi MichaIng, thanks a lot for your help.
Finally my i2c display was broken, when I replaced it, everything works like expected.

[MichaIng]

Okay great that it finally works 🙂.