Implement device wipe using the hardware button on Green

Unlike Yellow, Green doesn't have a way to easily wipe the device, e.g. if the
user forgets the password - in that case the only option is to use a microSD
card and reflash the system. Fortunately, Green has a hardware button wired to
the PMIC chip which exposes the button state in one of the registers. Read this
value in U-Boot and decide if cmdline flag for device wipe should be set - same
as we do on Yellow.

Also enable LED driver and command in U-Boot. In the current implementation, if
the button is held for ~5 seconds when plugging in the device (this time
includes DDR training, SPL, etc.), the yellow LED turns solid to indicate wipe
is about the start. When the Linux kernel starts, the kernel LED driver takes
over and starts blinking in heartbeat pattern. Because it takes a while to load
the kernel, the LED stays solid for 2-3 seconds, which should be enough to
recognize it was acknowledged.

buildroot-external/board/nabucasa/green/uboot-boot.ush

@@ -27,6 +27,30 @@ test -n "${MACHINE_ID}" || setenv BOOT_CONDITION "systemd.condition-first-boot=t
 # HassOS bootargs
 setenv bootargs_hassos "zram.enabled=1 zram.num_devices=3 rootwait systemd.machine_id=${MACHINE_ID} fsck.repair=yes ${BOOT_CONDITION}"
 
+# Check if button is held for device wipe
+setenv counter 0
+i2c dev 0
+while test ${counter} -lt 2; do
+  i2c read 0x20 0xf0.1 1 ${loadaddr}
+  setexpr PWRON_STS *${loadaddr} \& 0x80
+
+  if test ${PWRON_STS} -eq 0x0; then
+    echo "Reset button pressed for ${counter} seconds"
+    setexpr counter ${counter} + 1
+
+    if test ${counter} -eq 2; then
+      echo "Proceeding with device wipe"
+      led user on
+      setenv bootargs_hassos "${bootargs_hassos} haos.wipe=1"
+    else
+      sleep 1
+    fi
+  else
+    # U-Boot has no break statement :')
+    setenv counter 2
+  fi
+done
+
 # HassOS system A/B
 setenv bootargs_a "root=PARTUUID=8d3d53e3-6d49-4c38-8349-aff6859e82fd ro"
 setenv bootargs_b "root=PARTUUID=a3ec664e-32ce-4665-95ea-7ae90ce9aa20 ro"

buildroot-external/board/nabucasa/green/uboot.config

@@ -0,0 +1,3 @@
+CONFIG_LED=y
+CONFIG_LED_GPIO=y
+CONFIG_CMD_LED=y

buildroot-external/configs/green_defconfig

@@ -143,7 +143,7 @@ BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2024.01"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="green"
-BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="$(BR2_EXTERNAL_HASSOS_PATH)/bootloader/uboot.config"
+BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="$(BR2_EXTERNAL_HASSOS_PATH)/bootloader/uboot.config $(BR2_EXTERNAL_HASSOS_PATH)/board/nabucasa/green/uboot.config"
 BR2_TARGET_UBOOT_NEEDS_PYLIBFDT=y
 BR2_TARGET_UBOOT_NEEDS_PYELFTOOLS=y
 BR2_TARGET_UBOOT_NEEDS_ATF_BL31=y