HLK-7688a pin functions - how to switch

Hardware Questions and Recommendations
1

We're using the Hilink HLK-7688a and openwrt 23.05.2. I've found similar questions and responses for what I need on this forum relative to pin functions, but they're mostly on "what" to do and not specifically "how". All the things I've tried so far seem to be unsuccessful. Being new to this, it would be extremely helpful to have the "how" provided with examples. I'm still getting up to speed on this architecture and syntax used within DTS files and from what I understand about all this, this is what will setup the 7688.

The pins for lan3 and 4 ports are multiplexed as SD mode pins. We need to set the pin functions to SD.

We need to have the pins for lan1 port set to GPIO.

From what I understand from Hilink, the 4 lan ports with the mux function is such that you either get all 4 ports or they are all set as muxed functions. If they are set to the other functions, only the WAN port is available for ethernet.
Toradex has a very good writeup on DTS files, but I'm still not fully understanding the concepts that would help in the 7688 case.

The mediatek 7688 datasheet indicates to set the lan3,4 port pins as SD_MODE, you set registers EPHY_APGIO_AIO_EN[4:1] =4’b1111 and SD_MODE =2’b00. How does that correlate to DTS files?

The datasheet also specifies SDXC / eMMC is at memory range 1013.0000 - 1013.7FFF. From what I see in the mt7628an DTS file, it defines "sdhci: mmc@10130000 {". I just don't understand the syntax of items like sdhci, sdxc, sdxc_pins, where labels like "sdmode", "pwm0", etc, are defined so I'd know how to use them?

The DTS file that needs updating for what we need is mt7628an_hilink_hlk-7688a.dts, which includes mt7628an.dtsi.

What I'm hoping to achieve:

  1. Can someone who knows how to do this please explain, with specific examples, what it takes to turn those lan3,4 port pins into SD mode, turn the lan1 port into GPIO, and maybe provide a resource to help understand what names are used throughout the dts world of syntax?

  2. Then, is there any way to verify the pins are doing what they're supposed to do? Onion has a tool, omega2-ctrl, to identify the pin functions when the firmware is on the device but it looks like hilink doesn't. Is there such a generic tool?

2

Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button:
grafik
Remember to redact passwords, MAC addresses and any public IP addresses you may have:

ubus call system board
3 
{
        "kernel": "5.15.137",
        "hostname": "OpenWrt",
        "system": "MediaTek MT7688 ver:1 eco:2",
        "model": "<model redacted>",
        "board_name": "hilink,hlk-7688a",
        "rootfs_type": "squashfs",
        "release": {
                "distribution": "OpenWrt",
                "version": "23.05.2",
                "revision": "unknown",
                "target": "ramips/mt76x8",
                "description": "OpenWrt 23.05.2 <sdk version used>"
        }
}
4

Sorry, cant help when you clear most importand bits model and revision hash.