Set initial_turbo=0 in config.txt on Raspberry Pi 3 (#3973)

Firmware change that set initial_turbo to 60 from the previous 0 has broken
initialization of some SD cards in U-Boot. Adjust the value in config.txt on OS
update if the value is not already set by the user, and put it to the default
config.txt.

The config.txt also contains a short comment explaining the purpose. The
purpose of it is also to make it easier to revert this change in the future if
the problem is fixed in the firmware or U-Boot.

Fixes #3965

buildroot-external/board/raspberrypi/config.txt

@@ -71,6 +71,10 @@ kernel=u-boot.bin
 # Enable audio (loads snd_bcm2835)
 dtparam=audio=on
 
+[pi3]
+# Added to fix #3965
+initial_turbo=0
+
 [pi4]
 # Enable DRM VC4 V3D driver on top of the dispmanx display stack
 dtoverlay=vc4-fkms-v3d

buildroot-external/ota/rauc-hook

@@ -53,6 +53,21 @@ install_boot() {
         fi
     fi
 
+    # Fix for Pi3 not booting from some SD cards with now default initial_turbo=60
+    # see: https://github.com/home-assistant/operating-system/issues/3965
+    if [ "$RAUC_SYSTEM_COMPATIBLE" = "haos-rpi3" ] || [ "$RAUC_SYSTEM_COMPATIBLE" = "haos-rpi3-64" ]; then
+        # Don't change anything if initial_turbo is already set anywhere
+        if ! grep -q "^initial_turbo=" "${BOOT_MNT}/config.txt"; then
+            if grep -q '^\[pi3\]' "${BOOT_MNT}/config.txt"; then
+                echo "Adding initial_turbo=0 to [pi3] section of config.txt"
+                sed -i '/^\[pi3\]/a # Added to fix #3965\ninitial_turbo=0' "${BOOT_MNT}/config.txt"
+            else
+                echo "Adding [pi3] section with initial_turbo=0 to config.txt"
+                sed -i 's/^\[all\]/\[pi3\]\n# Added to fix #3965\ninitial_turbo=0\n\n\[all\]/' "${BOOT_MNT}/config.txt"
+            fi
+        fi
+    fi
+
     # Prepare rauc.db for migration, should be removed in HAOS 16
     # (along with raucdb-migrate.service and related raucdb-update changes)
     if [ -f /mnt/data/rauc.db ]; then