realtek: rtl930x: Add support for Plasma Cloud MCX3 Media Converter

realtek: rtl930x: Add support for Plasma Cloud MCX3 Media Converter

The Plasma Cloud MCX3 Media Converter is a 3 port multi-GBit switch with
2x 10/100/1000/2500BaseT Ethernet ports and 1x SFP+ module slot.

Hardware:

- RTL9302C SoC
- Macronix MX25L25645G (32MB flash)
- Winbond W632GU6rB-11 (256MB DDR3 SDRAM)
- RTL8224 4x 10m/100m/1/2.5 Gigabit PHY
- IC+ IP802AR POE+ PSE controller

The media converter is powered by 54 Volts 1.2A barrel connector. The
internal TTL serial connector can be used to access the terminal. Pins from
1: TX RX (unused) GND. Serial connection is via 115200 baud, 8N1.

A reset button is accessible through a hole next to the SFP+ module slot.

Installation
------------

* The device can be flashed by using sysupgrade command. Either from the
  original vendor firmware or using an initramfs (see "Debug")
* Connect serial as per the layout above. Connection parameters: 115200 8N1
* The image must be copied using scp to /tmp of the device

      scp openwrt-realtek-rtl930x-plasmacloud_mcx3-squashfs-sysupgrade.bin root@[IP address of the device]:/tmp/

* start sysupgrade without saving the original vendor configuration

      sysupgrade -n /tmp/openwrt-realtek-rtl930x-plasmacloud_mcx3-squashfs-sysupgrade.bin

Installation via u-boot
-----------------------

If you have an TFTP server connected to the switch, it is possible to
directly install the device using the factory image from u-boot

    # setup networking and IP of TFP server
    rtk network on
    setenv ipaddr 10.100.100.99
    setenv serverip 10.100.100.20

    # get factory image
    tftp 0x84000000 factory.bin

    # erase firmware partitions
    sf probe 0
    sf erase 0x100000 0x01f00000

    # write firmware to both partitions
    sf write ${fileaddr} 0x100000 ${filesize}
    sf write ${fileaddr} 0x1080000 ${filesize}

    # adjust the boot commands
    setenv bootargs "mtdparts=spi0.0:896k(u-boot),64k(u-boot-env),64k(u-boot-env2),15872k(inactive),15872k(firmware2)"
    setenv bootcmd "rtk init; bootm 0xb5080000"

    # restart
    reset

Debug
-----

* Connect serial as per the layout above. Connection parameters: 115200 8N1.
* A tftp server is required, tftpd-hpa works well.
* Power the device, at U-Boot start rapidly hit Esc key to stop autoboot
* Enable network:

      rtk network on

* Change ip address of device:

      setenv ipaddr 192.168.1.6

* Download initramfs from TFTP server:

      tftpboot 0x84000000 192.168.1.111:openwrt-realtek-rtl930x-plasmacloud_mcx3-initramfs-kernel.bin

* Boot loaded file:

      bootm 0x84000000

Signed-off-by: Harshal Gohel <[email protected]>
Signed-off-by: Sven Eckelmann <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20625
Signed-off-by: Robert Marko <[email protected]>