sifiveu: add new target for SiFive U-based boards

RISC-V is a new CPU architecture aimed to be fully free and open. This
target will add support for it, based on 5.15.

Supports running on:
 - HiFive Unleashed - FU540, first generation
 - HiFive Unmatched - FU740, current latest generation, PCIe

SD-card images are generated, where the partitions are required to have
specific type codes. As it is commonplace nowadays, OpenSBI is used as the
first stage, with U-boot following as the proper bootloader.

Specifications:

HiFive Unleashed:
 - CPU: SiFive FU540 quad-core RISC-V (U54, RV64IMAFDC or RV64GC)
 - Memory: 8Gb
 - Ethernet: 1x 10/100/1000
 - Console: via microUSB

HiFive Unmatched:
 - CPU: SiFive FU740 quad-core RISC-V (U74, RV64IMAFDCB or RV64GCB)
 - Memory: 16Gb
 - Ethernet: 1x 10/100/1000
 - USB: 4x USB 3.2
 - PCIe:  - 1x PCIe Gen3 x8
          - 1x M.2 key M (PCIe x4)
          - 1x M.2 Key E (PCIe x1 / USB2.0)
 - Console: via microUSB

Installation:
Standard SD-card installation via dd-ing the generated image to
an SD-card of at least 256Mb.

Signed-off-by: Zoltan HERPAI <wigyori@uid0.hu>

target/linux/sifiveu/base-files/lib/preinit/79_move_config

@@ -0,0 +1,19 @@
+# Copyright (C) 2012-2015 OpenWrt.org
+
+move_config() {
+	local partdev
+
+	. /lib/upgrade/common.sh
+
+	if export_bootdevice && export_partdevice partdev 3; then
+		if mount -t vfat -o rw,noatime "/dev/$partdev" /mnt; then
+			if [ -f "/mnt/$BACKUP_FILE" ]; then
+				mv -f "/mnt/$BACKUP_FILE" /
+			fi
+			umount /mnt
+		fi
+	fi
+}
+
+boot_hook_add preinit_mount_root move_config
+

target/linux/sifiveu/base-files/lib/upgrade/platform.sh

@@ -0,0 +1,86 @@
+platform_check_image() {
+	local diskdev partdev diff
+
+	export_bootdevice && export_partdevice diskdev 0 || {
+		echo "Unable to determine upgrade device"
+		return 1
+	}
+
+	get_partitions "/dev/$diskdev" bootdisk
+
+	#extract the boot sector from the image
+	get_image "$@" | dd of=/tmp/image.bs count=1 bs=512b 2>/dev/null
+
+	get_partitions /tmp/image.bs image
+
+	#compare tables
+	diff="$(grep -F -x -v -f /tmp/partmap.bootdisk /tmp/partmap.image)"
+
+	rm -f /tmp/image.bs /tmp/partmap.bootdisk /tmp/partmap.image
+
+	if [ -n "$diff" ]; then
+		echo "Partition layout has changed. Full image will be written."
+		ask_bool 0 "Abort" && exit 1
+		return 0
+	fi
+}
+
+platform_copy_config() {
+	local partdev
+
+	if export_partdevice partdev 3; then
+		mount -t vfat -o rw,noatime "/dev/$partdev" /mnt
+		cp -af "$UPGRADE_BACKUP" "/mnt/$BACKUP_FILE"
+		umount /mnt
+	fi
+}
+
+platform_do_upgrade() {
+	local diskdev partdev diff
+
+	export_bootdevice && export_partdevice diskdev 0 || {
+		echo "Unable to determine upgrade device"
+		return 1
+	}
+
+	sync
+
+	if [ "$UPGRADE_OPT_SAVE_PARTITIONS" = "1" ]; then
+		get_partitions "/dev/$diskdev" bootdisk
+
+		#extract the boot sector from the image
+		get_image "$@" | dd of=/tmp/image.bs count=1 bs=512b
+
+		get_partitions /tmp/image.bs image
+
+		#compare tables
+		diff="$(grep -F -x -v -f /tmp/partmap.bootdisk /tmp/partmap.image)"
+	else
+		diff=1
+	fi
+
+	if [ -n "$diff" ]; then
+		get_image "$@" | dd of="/dev/$diskdev" bs=4096 conv=fsync
+
+		# Separate removal and addtion is necessary; otherwise, partition 1
+		# will be missing if it overlaps with the old partition 2
+		partx -d - "/dev/$diskdev"
+		partx -a - "/dev/$diskdev"
+
+		return 0
+	fi
+
+	#iterate over each partition from the image and write it to the boot disk
+	while read part start size; do
+		if export_partdevice partdev $part; then
+			echo "Writing image to /dev/$partdev..."
+			get_image "$@" | dd of="/dev/$partdev" ibs="512" obs=1M skip="$start" count="$size" conv=fsync
+		else
+			echo "Unable to find partition $part device, skipped."
+		fi
+	done < /tmp/partmap.image
+
+	#copy partition uuid
+	echo "Writing new UUID to /dev/$diskdev..."
+	get_image "$@" | dd of="/dev/$diskdev" bs=1 skip=440 count=4 seek=440 conv=fsync
+}