ipq40xx: add support for Cisco Meraki Z3C

ipq40xx: add support for Cisco Meraki Z3C

This commit adds support for the Meraki Z3C "Teleworker" device with
802.11ac, LTE Cat 3 modem, and an integrated 5 port Gigabit switch.

Port 5 has POE output (802.3af). The WAN port is used for tftp booting
in U-Boot.

This device ships with secure boot, and cannot be flashed without an
external programmer.

|||
|--|--|
|Model|Z3C|
|CPU|Qualcomm Atheros IPQ4029|
|Flash MB|128 NAND|
|RAM MB|512|
|WLAN Hardware|Qualcomm Atheros IPQ4029|
|WLAN 2.4GHz|b/g/n 2x2|
|WLAN 5.0GHz|a/n/ac 2x2|
|WWAN|LTE Cat 3|
|Ethernet 1Gbit ports|5|

The LAN/WiFi MAC addresses are sourced from an internal I2C EEPROM.

Z3C-HW-NA (NA: North America) supports LTE bands: 2,4,5,13,17

Z3C-HW-WW (WW: World-wide) supports LTE bands: 1,3,7,8,20

Disassembly:

Remove the four T8 screws on the bottom of the device under the rubber feet.

Using a guitar pick or similar plastic tool, insert it on the side between
the bottom case and the side, pry up gently. The plastic bottom has 18 latches
around the perimeter (but none on the rear by the Ethernet ports).
Remember to remove the SIM tray!

Gently remove the metal RF shield on the bottom of the PCB.

The TSOP48 NAND flash (U30, Spansion S34ML01G200TFV00) is located on the bottom
side of the PCB (facing you as you remove the bottom plastic). To flash, you
will need to desolder the TSOP48. Attempts to flash in-circuit using a 360 clip
were unsuccessful.

The SOIC8 I2C EEPROM (U32, Atmel 24C64) is located on the bottom side of the PCB
under a metal RF shield. It can be flashed in circuit using a chip clip. You may
have to bend the RF shield up to fit the chip clip.

The UART header is on the top (opposite) side of the PCB. You do not need to
remove any more screws to remove the PCB. The PCB has some thermal interface
material for heat dissipation and will be slightly difficult to remove the
first time. Gently pry up on the green PCB from one of the front corners until
the thermal pads break contact with the top case. You can then lift out the
entire PCB, including the attached LTE/WiFi antennas.

Installation:

The dumps to flash can be found in this repository:
https://github.com/halmartin/meraki-openwrt-docs/tree/main/z3c

The device has the following flash layout (offsets with OOB data):
```
0x000000000000-0x000000100000 : "sbl1"
0x000000100000-0x000000200000 : "mibib"
0x000000200000-0x000000300000 : "bootconfig"
0x000000300000-0x000000400000 : "qsee"
0x000000400000-0x000000500000 : "qsee_alt"
0x000000500000-0x000000580000 : "cdt"
0x000000580000-0x000000600000 : "cdt_alt"
0x000000600000-0x000000680000 : "ddrparams"
0x000000700000-0x000000900000 : "u-boot"
0x000000900000-0x000000b00000 : "u-boot-backup"
0x000000b00000-0x000000b80000 : "ART"
0x000000c00000-0x000007c00000 : "ubi"
```

* Dump your original NAND (if using nanddump, include OOB data).

* Decompress `u-boot.bin.gz` dump (contains OOB data) and overwrite the
`u-boot` portion of NAND from `0x738000-0x948000` (length `0x210000`).

* Decompress `ubi.bin.gz` dump (contains OOB data) and overwrite the `ubi`
portion of NAND from `0xc60000-0x8400000` (length `0x77a0000`).

* Dump your original EEPROM. Change the byte at offset `0x49` to `0x1e`
(originally `0x2a`). Remember to re-write the EEPROM with the
modified data.

* This can be done on Linux via the following command:
`printf "\x1e" | dd of=/tmp/eeprom.bin bs=1 seek=$((0x49)) conv=notrunc`

**Note**: the device will not boot if you modify the board major number and
have not yet overwritten the `ubi` and `u-boot` regions of NAND.

* Resolder the NAND after overwriting the `u-boot` and `ubi` regions.

OpenWrt Installation:

* After flashing NAND and EEPROM with external programmers. Plug in an
Ethernet cable and power up the device.

* The new U-Boot build uses the space character `" "` (without quotes) to
interrupt boot.

* Interrupt U-Boot and `tftpboot` the OpenWrt initramfs image from your
tftp server
```
dhcp
setenv serverip <your_tftp>
tftpboot openwrt-ipq40xx-generic-meraki_z3c-initramfs-uImage.itb
```

* Once booted into the OpenWrt initramfs, created the `ART` ubivol with
the WiFi radio calibration from the mtd partition:
```
cat /dev/mtd10 > /tmp/ART.bin
ubiupdatevol /dev/ubi0_1 /tmp/ART.bin
```

* `scp` the `sysupgrade` image to
the device and run the normal `sysupgrade` procedure:
```
scp -O openwrt-ipq40xx-generic-meraki_z3c-squashfs-sysupgrade.bin root@192.168.1.1:/tmp/
ssh root@192.168.1.1 "sysupgrade -n /tmp/openwrt-ipq40xx-generic-meraki_z3c-squashfs-sysupgrade.bin"
```

* OpenWrt should now be installed on the device.

* Note: To use the LTE modem as a WWAN, you must install `modemmanager`
(you probably also want `luci-proto-modemmanager`) and then configure
the modem for your provider.
Due to OpenWrt policies these packages are not included in the
initramfs/sysupgrade image.

Signed-off-by: Hal Martin <hal.martin@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/23307
Signed-off-by: Robert Marko <robimarko@gmail.com>