bcm27xx: add support for Raspberry Pi Zero 2

Due to licensing uncertainty, we do not include the firmwares for the
wireless chips used in the Raspberry Pi Zero 2 W. To have working
wireless, follow the instructions below.

For people building their own images:

  mkdir -p files/lib/firmware/brcm
  wget -P files/lib/firmware/brcm/ https://github.com/RPi-Distro/firmware-nonfree/raw/bullseye/debian/config/brcm80211/brcm/brcmfmac43436-sdio.bin
  wget -P files/lib/firmware/brcm/ https://github.com/RPi-Distro/firmware-nonfree/raw/bullseye/debian/config/brcm80211/brcm/brcmfmac43436-sdio.txt
  wget -P files/lib/firmware/brcm/ https://github.com/RPi-Distro/firmware-nonfree/raw/bullseye/debian/config/brcm80211/brcm/brcmfmac43436s-sdio.bin
  wget -P files/lib/firmware/brcm/ https://github.com/RPi-Distro/firmware-nonfree/raw/bullseye/debian/config/brcm80211/brcm/brcmfmac43436s-sdio.txt

Now build the OpenWrt image as usual, and it will include the firmware
files in the correct location.

For people using ext4 images:

Write the ext4 image to the sdcard, then mount the 2nd partition and put
the firmware files from the links above in /lib/firmware/brcm relative
from the mount point where the partition is mounted.

For people using squashfs images:

Write the squashfs image to the sdcard, place it in the Raspberry Pi
Zero 2 W, boot it and wait for the overlay filesystem to be created.
Find the offset of the overlay filesystem in sysfs:

  # cat /sys/devices/virtual/block/loop0/loop/offset
  25755648

Shut down the device, unplug the power and move the SD card to a Linux
computer. Mount the 2nd partition of the sdcard as a loop device with
the offset found earlier.

  sudo mount /dev/sdh2 -o loop,offset=25755648 /mnt/temp

Put the firmware files from the links above in /upper/lib/firmware/brcm
relative to the mount point where the loop device is mounted.

Signed-off-by: Stijn Tintel <[email protected]>
Tested-by: Peter van Dijk <[email protected]>

target/linux/bcm27xx/base-files/etc/board.d/02_network

@@ -23,6 +23,7 @@ raspberrypi,model-b-rev2)
 	ucidef_set_interface_lan "eth0"
 	;;
 
+raspberrypi,model-zero-2 |\
 raspberrypi,model-zero-w)
 	ucidef_set_interface_lan "wlan0"
 	;;

target/linux/bcm27xx/base-files/etc/diag.sh

@@ -20,6 +20,7 @@ set_state() {
 	raspberrypi,3-compute-module |\
 	raspberrypi,model-b |\
 	raspberrypi,model-zero |\
+	raspberrypi,model-zero-2 |\
 	raspberrypi,model-zero-w)
 		status_led="led0"
 		;;

target/linux/bcm27xx/image/Makefile

@@ -96,13 +96,15 @@ define Device/rpi-2
 	bcm2709-rpi-2-b bcm2710-rpi-2-b \
 	bcm2710-rpi-3-b bcm2710-rpi-3-b-plus \
 	bcm2711-rpi-4-b bcm2711-rpi-400 \
-	bcm2710-rpi-cm3 bcm2711-rpi-cm4
+	bcm2710-rpi-cm3 bcm2711-rpi-cm4 \
+	bcm2710-rpi-zero-2
   SUPPORTED_DEVICES := \
-	rpi-2-b rpi-3-b rpi-3-b-plus rpi-cm \
+	rpi-2-b rpi-3-b rpi-3-b-plus rpi-cm rpi-zero-2 \
 	raspberrypi,2-model-b raspberrypi,2-model-b-rev2 \
 	raspberrypi,3-model-b raspberrypi,3-model-b-plus \
 	raspberrypi,3-compute-module raspberrypi,compute-module-3 \
-	raspberrypi,400 raspberrypi,4-compute-module raspberrypi,4-model-b
+	raspberrypi,400 raspberrypi,4-compute-module raspberrypi,4-model-b \
+	raspberrypi,model-zero-2
   DEVICE_PACKAGES := \
 	cypress-firmware-43430-sdio \
 	cypress-nvram-43430-sdio-rpi-3b \
@@ -126,12 +128,14 @@ define Device/rpi-3
   DEVICE_DTS := \
 	broadcom/bcm2710-rpi-2-b \
 	broadcom/bcm2710-rpi-3-b broadcom/bcm2710-rpi-3-b-plus \
-	broadcom/bcm2710-rpi-cm3
+	broadcom/bcm2710-rpi-cm3 \
+	broadcom/bcm2710-rpi-zero-2
   SUPPORTED_DEVICES := \
-	rpi-3-b rpi-3-b-plus \
+	rpi-3-b rpi-3-b-plus rpi-zero-2 \
 	raspberrypi,2-model-b-rev2 \
 	raspberrypi,3-model-b raspberrypi,3-model-b-plus \
-	raspberrypi,3-compute-module raspberrypi,compute-module-3
+	raspberrypi,3-compute-module raspberrypi,compute-module-3 \
+	raspberrypi,model-zero-2
   DEVICE_PACKAGES := \
 	cypress-firmware-43430-sdio \
 	cypress-nvram-43430-sdio-rpi-3b \