mtd: base-files: Unify dual-firmware devices (Linksys)

Consistently handle boot-count reset and upgrade across
ipq40xx, ipq806x, kirkwood, mvebu

Dual-firmware devices often utilize a specific MTD partition
to record the number of times the boot loader has initiated boot.

Most of these devices are NAND, typically with a 2k erase size.
When this code was ported to the ipq40xx platform, the device in hand
used NOR for this partition, with a 16-byte "record" size. As the
implementation of `mtd resetbc` is by-platform, the hard-coded nature
of this change prevented proper operation of a NAND-based device.

* Unified the "NOR" variant with the rest of the Linksys variants

* Added logging to indicate success and failure

* Provided a meaningful return value for scripting

* "Protected" the use of `mtd resetbc` in start-up scripts so that
   failure does not end the boot sequence

* Moved Linksys-specific actions into common `/etc/init.d/bootcount`

For upgrade, these devices need to determine which partition to flash,
as well as set certain U-Boot envirnment variables to change the next
boot to the newly flashed version.

* Moved upgrade-related environment changes out of bootcount

* Combined multiple flashes of environment into single one

* Current-partition detection now handles absence of `boot_part`

Runtime-tested: Linksys EA8300

Signed-off-by: Jeff Kletsky <git-commits@allycomm.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
[checkpatch.pl fixes, traded split strings for 80+ chars per line]

target/linux/ipq806x/base-files/lib/upgrade/linksys.sh

@@ -3,28 +3,47 @@
 #
 
 linksys_get_target_firmware() {
-	cur_boot_part=`/usr/sbin/fw_printenv -n boot_part`
-	target_firmware=""
-	if [ "$cur_boot_part" = "1" ]
-	then
-		# current primary boot - update alt boot
-		target_firmware="kernel2"
-		fw_setenv boot_part 2
-		#In EA8500 bootcmd is always "bootipq", so don't change
-		#fw_setenv bootcmd "run altnandboot"
-	elif [ "$cur_boot_part" = "2" ]
-	then
-		# current alt boot - update primary boot
-		target_firmware="kernel1"
-		fw_setenv boot_part 1
-		#In EA8500 bootcmd is always "bootipq", so don't change
-		#fw_setenv bootcmd "run nandboot"
+
+	local cur_boot_part mtd_ubi0
+
+	cur_boot_part=$(/usr/sbin/fw_printenv -n boot_part)
+	if [ -z "${cur_boot_part}" ] ; then
+		mtd_ubi0=$(cat /sys/devices/virtual/ubi/ubi0/mtd_num)
+		case $(egrep ^mtd${mtd_ubi0}: /proc/mtd | cut -d '"' -f 2) in
+		kernel1|rootfs1)
+			cur_boot_part=1
+			;;
+		kernel2|rootfs2)
+			cur_boot_part=2
+			;;
+		esac
+		>&2 printf "Current boot_part='%s' selected from ubi0/mtd_num='%s'" \
+			"${cur_boot_part}" "${mtd_ubi0}"
 	fi
 
-	# re-enable recovery so we get back if the new firmware is broken
-	fw_setenv auto_recovery yes
+	cur_boot_part=`/usr/sbin/fw_printenv -n boot_part`
 
-	echo "$target_firmware"
+	case $cur_boot_part in
+	1)
+		fw_setenv -s - <<-EOF
+			boot_part 2
+			auto_recovery yes
+		EOF
+		printf "kernel2"
+		return
+		;;
+	2)
+		fw_setenv -s - <<-EOF
+			boot_part 1
+			auto_recovery yes
+		EOF
+		printf "kernel1"
+		return
+		;;
+	*)
+		return
+		;;
+	esac
 }
 
 linksys_get_root_magic() {