[v3,6/7] board: Add Sipeed MAIX-Go board support

diff --git a/DEVELOPERS b/DEVELOPERS
index 4a25418695..0116ab0815 100644
--- a/DEVELOPERS
+++ b/DEVELOPERS
@@ -640,6 +640,8 @@  F:	configs/sipeed_maixduino_defconfig
 F:	configs/sipeed_maixduino_sdcard_defconfig
 F:	configs/sipeed_maix_dock_defconfig
 F:	configs/sipeed_maix_dock_sdcard_defconfig
+F:	configs/sipeed_maix_go_defconfig
+F:	configs/sipeed_maix_go_sdcard_defconfig
 
 N:	Daniel Nicoletti <dantti12@gmail.com>
 F:	package/cutelyst/
diff --git a/board/sipeed/maix-go/linux-cpio.config b/board/sipeed/maix-go/linux-cpio.config
new file mode 100644
index 0000000000..ea8c30e266
--- /dev/null
+++ b/board/sipeed/maix-go/linux-cpio.config
@@ -0,0 +1,2 @@ 
+CONFIG_SOC_CANAAN_K210_DTB_BUILTIN=y
+CONFIG_SOC_CANAAN_K210_DTB_SOURCE="sipeed_maix_go"
diff --git a/board/sipeed/maix-go/readme.txt b/board/sipeed/maix-go/readme.txt
new file mode 100644
index 0000000000..9f930fb6ac
--- /dev/null
+++ b/board/sipeed/maix-go/readme.txt
@@ -0,0 +1,320 @@ 
+Sipeed MAIX-Go Board
+====================
+
+The Sipeed MAXI-Go board is a dual-core RISC-V 64-bits board based on the
+Canaan Kendryte K210 SoC.
+
+Prerequisite
+------------
+
+In order to use the kflash utility to program this board, the user must have
+access to the board USB serial device file. The simplest way to do this is to
+add your user to the same group as this device file. Assume the device file is
+/dev/ttyUSB0, first identify the device group name. In most cases, it is
+either "dialout" or "uucp". Also verify that read-write access is enabled for
+the group:
+
+```
+$ ls -l /dev/ttyUSB0
+crw-rw---- 1 root dialout 188, 0 May 26 13:48 /dev/ttyUSB0
+```
+
+Then add yourself to that group (dialout in this example):
+
+```
+$ sudo usermod -a -G dialout $(whoami)
+```
+
+To enable the above, it is sometimes necessary to logout and login again.
+
+Buildroot Configuration
+-----------------------
+
+Two buildroot configuration files are provided:
+
+(1) Direct Linux Kernel Boot
+
+This is defined by the sipeed_maix_go_defconfig configuration. This
+configuration allows building a bootable kernel image with a built-in initramfs
+root file system (the board SD card is not used). The built kernel image can be
+flashed directly to the board ROM for direct booting. No boot loader is
+required.
+
+(2) U-Boot SD-Card Boot
+
+The sipeed_maix_go_sdcard_defconfig configuration allows building a kernel
+image with the root file system on the board SD card. U-Boot is used as the
+boot loader.
+
+Note: U-Boot does not natively support the Sipeed MAIX-Go board. However, the
+board and device tree differences with the Sipeed MAIX-bit board are small
+enough for U-Boot to work.
+
+Both configuration files will also compile and install the kflash and
+pyserial-miniterm host utilities to program bootable image files to the board
+and open a serial terminal console.
+
+Direct Linux Kernel Boot
+-------------------------
+
+Using the sipeed_maix_go_defconfig configuration, the bootable kernel binary
+image is built as follows.
+
+```
+$ make sipeed_maix_go_defconfig
+$ make
+```
+
+The bootable binary image is the output/images/loader.bin file. This image file
+can be written to the board boot flash using the kflash utility.
+
+```
+$ output/host/bin/kflash -b 1500000 -p /dev/ttyUSB0 -t output/images/loader.bin
+```
+
+Once the kernel image file is fully programmed, a terminal console is open and
+the board can be rebooted by pressing the reset button on the board (if it does
+not reboot automatically).
+
+The output will be similar to the following.
+
+```
+[    0.000000] Linux version 5.17.0 (foo@bar.com) (riscv64-buildroot-linux-uclibc-gcc.br_real (Buildroot 2022.02-560-g6a2b542a09-dirty) 10.3.0, GNU ld (GNU Binutils) 2.32) #2 SMP Thu Apr 21 16:09:24 JST 2022
+[    0.000000] Machine model: SiPeed MAIX GO
+[    0.000000] earlycon: sifive0 at MMIO 0x0000000038000000 (options '115200n8')
+[    0.000000] printk: bootconsole [sifive0] enabled
+[    0.000000] Zone ranges:
+[    0.000000]   DMA32    [mem 0x0000000080000000-0x00000000807fffff]
+[    0.000000]   Normal   empty
+[    0.000000] Movable zone start for each node
+[    0.000000] Early memory node ranges
+[    0.000000]   node   0: [mem 0x0000000080000000-0x00000000807fffff]
+[    0.000000] Initmem setup node 0 [mem 0x0000000080000000-0x00000000807fffff]
+[    0.000000] riscv: ISA extensions acdfim
+[    0.000000] riscv: ELF capabilities acdfim
+[    0.000000] percpu: max_distance=0x16000 too large for vmalloc space 0x0
+[    0.000000] percpu: Embedded 11 pages/cpu s15264 r0 d29792 u45056
+[    0.000000] percpu: wasting 10 pages per chunk
+[    0.000000] Built 1 zonelists, mobility grouping off.  Total pages: 2020
+[    0.000000] Kernel command line: earlycon console=ttySIF0
+[    0.000000] Dentry cache hash table entries: 1024 (order: 1, 8192 bytes, linear)
+[    0.000000] Inode-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
+[    0.000000] Memory: 5980K/8192K available (964K kernel code, 137K rwdata, 205K rodata, 546K init, 66K bss, 2212K reserved, 0K cma-reserved)
+[    0.000000] rcu: Hierarchical RCU implementation.
+[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
+[    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
+[    0.000000] riscv-intc: 64 local interrupts mapped
+[    0.000000] plic: interrupt-controller@c000000: mapped 65 interrupts with 2 handlers for 4 contexts.
+[    0.000000] k210-clk: clock-controller: CPU running at 390 MHz
+[    0.000000] clint: timer@2000000: timer running at 7800000 Hz
+[    0.000000] clocksource: clint_clocksource: mask: 0xffffffffffffffff max_cycles: 0x3990be68b, max_idle_ns: 881590404272 ns
+[    0.000001] sched_clock: 64 bits at 7MHz, resolution 128ns, wraps every 4398046511054ns
+[    0.008193] Calibrating delay loop (skipped), value calculated using timer frequency.. 15.60 BogoMIPS (lpj=31200)
+[    0.018250] pid_max: default: 4096 minimum: 301
+[    0.022862] Mount-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+[    0.029971] Mountpoint-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+[    0.040239] rcu: Hierarchical SRCU implementation.
+[    0.045118] smp: Bringing up secondary CPUs ...
+[    0.050204] smp: Brought up 1 node, 2 CPUs
+[    0.054336] devtmpfs: initialized
+[    0.071519] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
+[    0.080591] pinctrl core: initialized pinctrl subsystem
+[    0.121163] clocksource: Switched to clocksource clint_clocksource
+[    0.133221] workingset: timestamp_bits=62 max_order=11 bucket_order=0
+[    0.180960] k210-sysctl 50440000.syscon: K210 system controller
+[    0.196811] k210-rst 50440000.syscon:reset-controller: K210 reset controller
+[    0.204879] cacheinfo: Unable to detect cache hierarchy for CPU 0
+[    0.214087] i2c_dev: i2c /dev entries driver
+[    0.222736] k210-fpioa 502b0000.pinmux: K210 FPIOA pin controller
+[    0.236173] 38000000.serial: ttySIF0 at MMIO 0x38000000 (irq = 1, base_baud = 115200) is a SiFive UART v0
+[    0.245104] printk: console [ttySIF0] enabled
+[    0.245104] printk: console [ttySIF0] enabled
+[    0.253726] printk: bootconsole [sifive0] disabled
+[    0.253726] printk: bootconsole [sifive0] disabled
+[    0.265588] panel@0 enforce active low on chipselect handle
+[    0.282358] Freeing unused kernel image (initmem) memory: 540K
+[    0.287492] This architecture does not have kernel memory protection.
+[    0.293926] Run /init as init process
+          __  _
+         / / (_) ____   _   _ __  __
+        / /  | ||  _ \ | | | |\ \/ /
+       / /___| || | | || |_| | >  <
+      /_____/|_||_| |_| \____|/_/\_\
+    64-bits RISC-V Kendryte K210 NOMMU
+
+/ #
+```
+
+To open a terminal console without re-flashing the board, the pyserial-miniterm
+host tool can be used.
+
+```
+$ output/host/bin/pyserial-miniterm --raw --eol=LF /dev/ttyUSB0 115200
+```
+
+The options "--raw" and "--eol=LF" are added here to avoid a double carriage
+return each time a command is entered.
+
+
+U-Boot SD-Card Boot
+-------------------
+
+The build procedure is similar to the built-in initramfs case.
+
+```
+$ make sipeed_maix_go_sdcard_defconfig
+$ make
+```
+
+The build process will generate two files under the output/images directory.
+
+* sdcard.img: The image file for the SD card filesystem. This image has 2
+  partitions. The first partition is a vfat partition containing the kernel
+  uImage and the board device tree binary. The second partition is the root
+  filesystem with busybox installed. The second partition is formatted using
+  ext2 (rev1).
+
+* uboot.bin: U-Boot bootable binary to load and boot the kernel from the SD
+  card.
+
+The SD card can be prepared by writing the sdcard.img file, as follows.
+
+```
+$ sudo dd if=output/images/sdcard.img of=/dev/sdX bs=1M
+$ sync
+$ eject /dev/sdX
+```
+
+Where /dev/sdX is the device file name of the SD card. Once completed, the SD
+card can be inserted into the board and the U-Boot binary image written to the
+board boot flash using the kflash utility.
+
+```
+$ output/host/bin/kflash -b 1500000 -p /dev/ttyUSB0 -t output/images/u-boot.bin
+```
+
+The above command will program U-Boot image to the board boot ROM and open a
+terminal console once the u-boot.bin file is fully programmed. Reboot into the
+newly programmed environment by pressing the board reset button.
+
+The output will be similar to the following.
+
+```
+U-Boot 2022.04 (Apr 21 2022 - 16:28:58 +0900)
+
+DRAM:  8 MiB
+Core:  34 devices, 17 uclasses, devicetree: separate
+WDT:   Not starting watchdog@50400000
+MMC:   spi@53000000:slot@0: 0
+Loading Environment from SPIFlash... SF: Detected gd25lq128 with page size 256 Bytes, erase size 4 KiB, total 16 MiB
+*** Warning - bad CRC, using default environment
+
+In:    serial@38000000
+Out:   serial@38000000
+Err:   serial@38000000
+Hit any key to stop autoboot:  0
+1717730 bytes read in 956 ms (1.7 MiB/s)
+10502 bytes read in 11 ms (931.6 KiB/s)
+## Booting kernel from Legacy Image at 80060000 ...
+   Image Name:   Linux
+   Image Type:   RISC-V Linux Kernel Image (uncompressed)
+   Data Size:    1717666 Bytes = 1.6 MiB
+   Load Address: 80000000
+   Entry Point:  80000000
+   Verifying Checksum ... OK
+## Flattened Device Tree blob at 80400000
+   Booting using the fdt blob at 0x80400000
+   Loading Kernel Image
+   Loading Device Tree to 00000000803fa000, end 00000000803ff905 ... OK
+
+Starting kernel ...
+
+[    0.000000] Linux version 5.17.0 (foo@bar.com) (riscv64-buildroot-linux-uclibc-gcc.br_real (Buildroot 2022.02-560-g6a2b542a09-dirty) 10.3.0, GNU ld (GNU Binutils) 2.32) #1 SMP Thu Apr 21 16:29:10 JST 2022
+[    0.000000] Machine model: SiPeed MAIX GO
+[    0.000000] earlycon: sifive0 at MMIO 0x0000000038000000 (options '115200n8')
+[    0.000000] printk: bootconsole [sifive0] enabled
+[    0.000000] Zone ranges:
+[    0.000000]   DMA32    [mem 0x0000000080000000-0x00000000807fffff]
+[    0.000000]   Normal   empty
+[    0.000000] Movable zone start for each node
+[    0.000000] Early memory node ranges
+[    0.000000]   node   0: [mem 0x0000000080000000-0x00000000807fffff]
+[    0.000000] Initmem setup node 0 [mem 0x0000000080000000-0x00000000807fffff]
+[    0.000000] riscv: ISA extensions acdfim
+[    0.000000] riscv: ELF capabilities acdfim
+[    0.000000] percpu: max_distance=0x16000 too large for vmalloc space 0x0
+[    0.000000] percpu: Embedded 11 pages/cpu s15392 r0 d29664 u45056
+[    0.000000] percpu: wasting 10 pages per chunk
+[    0.000000] Built 1 zonelists, mobility grouping off.  Total pages: 2020
+[    0.000000] Kernel command line: earlycon console=ttySIF0 root=/dev/mmcblk0p2 rootwait ro
+[    0.000000] Dentry cache hash table entries: 1024 (order: 1, 8192 bytes, linear)
+[    0.000000] Inode-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
+[    0.000000] Memory: 6156K/8192K available (1180K kernel code, 151K rwdata, 239K rodata, 102K init, 69K bss, 2036K reserved, 0K cma-reserved)
+[    0.000000] rcu: Hierarchical RCU implementation.
+[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
+[    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
+[    0.000000] riscv-intc: 64 local interrupts mapped
+[    0.000000] plic: interrupt-controller@c000000: mapped 65 interrupts with 2 handlers for 4 contexts.
+[    0.000000] k210-clk: clock-controller: CPU running at 390 MHz
+[    0.000000] clint: timer@2000000: timer running at 7800000 Hz
+[    0.000000] clocksource: clint_clocksource: mask: 0xffffffffffffffff max_cycles: 0x3990be68b, max_idle_ns: 881590404272 ns
+[    0.000001] sched_clock: 64 bits at 7MHz, resolution 128ns, wraps every 4398046511054ns
+[    0.008201] Calibrating delay loop (skipped), value calculated using timer frequency.. 15.60 BogoMIPS (lpj=31200)
+[    0.018256] pid_max: default: 4096 minimum: 301
+[    0.022875] Mount-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+[    0.029983] Mountpoint-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+[    0.040405] rcu: Hierarchical SRCU implementation.
+[    0.045387] smp: Bringing up secondary CPUs ...
+[    0.050501] smp: Brought up 1 node, 2 CPUs
+[    0.054662] devtmpfs: initialized
+[    0.072840] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
+[    0.081918] pinctrl core: initialized pinctrl subsystem
+[    0.124601] clocksource: Switched to clocksource clint_clocksource
+[    0.137869] workingset: timestamp_bits=62 max_order=11 bucket_order=0
+[    0.183507] k210-sysctl 50440000.syscon: K210 system controller
+[    0.199987] k210-rst 50440000.syscon:reset-controller: K210 reset controller
+[    0.209219] cacheinfo: Unable to detect cache hierarchy for CPU 0
+[    0.221062] i2c_dev: i2c /dev entries driver
+[    0.232254] k210-fpioa 502b0000.pinmux: K210 FPIOA pin controller
+[    0.245342] 38000000.serial: ttySIF0 at MMIO 0x38000000 (irq = 1, base_baud = 115200) is a SiFive UART v0
+[    0.254281] printk: console [ttySIF0] enabled
+[    0.254281] printk: console [ttySIF0] enabled
+[    0.262908] printk: bootconsole [sifive0] disabled
+[    0.262908] printk: bootconsole [sifive0] disabled
+[    0.274939] panel@0 enforce active low on chipselect handle
+[    0.308760] mmc_spi spi3.0: SD/MMC host mmc0, no WP, no poweroff, cd polling
+[    0.321220] Waiting for root device /dev/mmcblk0p2...
+[    0.344805] mmc0: host does not support reading read-only switch, assuming write-enable
+[    0.352142] mmc0: new SDHC card on SPI
+[    0.358622] mmcblk0: mmc0:0000 SA16G 14.5 GiB
+[    0.366636] random: fast init done
+[    0.371323]  mmcblk0: p1 p2
+[    0.392887] random: get_random_bytes called from 0x000000008009b7d2 with crng_init=1
+[    0.394338] VFS: Mounted root (ext2 filesystem) readonly on device 179:2.
+[    0.411277] devtmpfs: mounted
+[    0.413836] Freeing unused kernel image (initmem) memory: 96K
+[    0.419267] This architecture does not have kernel memory protection.
+[    0.425683] Run /sbin/init as init process
+[    0.594251] random: crng init done
+          __  _
+         / / (_) ____   _   _ __  __
+        / /  | ||  _ \ | | | |\ \/ /
+       / /___| || | | || |_| | >  <
+      /_____/|_||_| |_| \____|/_/\_\
+    64-bits RISC-V Kendryte K210 NOMMU
+
+/ #
+```
+
+Of note is that the kernel mounts the SD card as read-only by default to avoid
+corruptions of the ext2 root file system when the board is powered down. This
+is recommended as this board does not support clean shutdown or halt.
+
+Similarly to the initramfs build case, a console can be open without
+re-flashing the board using the host tool pyserial-miniterm.
+
+```
+$ output/host/bin/pyserial-miniterm --raw --eol=LF /dev/ttyUSB0 115200
+```
diff --git a/configs/sipeed_maix_go_defconfig b/configs/sipeed_maix_go_defconfig
new file mode 100644
index 0000000000..2054e49ae2
--- /dev/null
+++ b/configs/sipeed_maix_go_defconfig
@@ -0,0 +1,39 @@ 
+# Architecture
+BR2_riscv=y
+BR2_RISCV_64=y
+BR2_riscv_custom=y
+BR2_RISCV_ISA_CUSTOM_RVM=y
+BR2_RISCV_ISA_CUSTOM_RVA=y
+BR2_RISCV_ISA_CUSTOM_RVF=y
+BR2_RISCV_ISA_CUSTOM_RVD=y
+BR2_RISCV_ISA_CUSTOM_RVC=y
+BR2_RISCV_ABI_LP64D=y
+
+# Patches
+BR2_GLOBAL_PATCH_DIR="board/riscv/nommu/patches"
+
+# Binary format
+# BR2_USE_MMU is not set
+BR2_BINFMT_FLAT=y
+BR2_BINFMT_FLAT_ONE=y
+# BR2_TARGET_ENABLE_ROOT_LOGIN is not set
+
+# Kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.18"
+BR2_LINUX_KERNEL_DEFCONFIG="nommu_k210"
+BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="board/sipeed/maix-go/linux-cpio.config"
+BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM=y
+BR2_LINUX_KERNEL_IMAGE_NAME="loader.bin"
+
+# Packages
+BR2_PACKAGE_HOST_PYTHON_KFLASH=y
+BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
+BR2_PACKAGE_BUSYBOX_CONFIG_FRAGMENT_FILES="board/canaan/k210-soc/busybox-tiny.config"
+# BR2_PACKAGE_IFUPDOWN_SCRIPTS is not set
+
+# Filesystem
+BR2_INIT_NONE=y
+BR2_TARGET_ROOTFS_INITRAMFS=y
+BR2_ROOTFS_OVERLAY="board/canaan/k210-soc/rootfs_overlay"
diff --git a/configs/sipeed_maix_go_sdcard_defconfig b/configs/sipeed_maix_go_sdcard_defconfig
new file mode 100644
index 0000000000..a16943608c
--- /dev/null
+++ b/configs/sipeed_maix_go_sdcard_defconfig
@@ -0,0 +1,57 @@ 
+# Architecture
+BR2_riscv=y
+BR2_RISCV_64=y
+BR2_riscv_custom=y
+BR2_RISCV_ISA_CUSTOM_RVM=y
+BR2_RISCV_ISA_CUSTOM_RVA=y
+BR2_RISCV_ISA_CUSTOM_RVF=y
+BR2_RISCV_ISA_CUSTOM_RVD=y
+BR2_RISCV_ISA_CUSTOM_RVC=y
+BR2_RISCV_ABI_LP64D=y
+
+# Patches
+BR2_GLOBAL_PATCH_DIR="board/riscv/nommu/patches"
+
+# System
+# BR2_USE_MMU is not set
+BR2_BINFMT_FLAT=y
+BR2_BINFMT_FLAT_ONE=y
+# BR2_TARGET_ENABLE_ROOT_LOGIN is not set
+
+# Kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.18"
+BR2_LINUX_KERNEL_DEFCONFIG="nommu_k210_sdcard"
+BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="board/canaan/k210-soc/linux-sdcard.config"
+BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM=y
+BR2_LINUX_KERNEL_IMAGE_NAME="loader.bin"
+BR2_LINUX_KERNEL_DTS_SUPPORT=y
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="canaan/sipeed_maix_go"
+
+# Packages
+BR2_PACKAGE_BUSYBOX_CONFIG="package/busybox/busybox-minimal.config"
+# BR2_PACKAGE_IFUPDOWN_SCRIPTS is not set
+
+# Filesystem
+BR2_INIT_NONE=y
+BR2_TARGET_ROOTFS_EXT2=y
+BR2_TARGET_ROOTFS_EXT2_SIZE=64M
+BR2_ROOTFS_OVERLAY="board/canaan/k210-soc/rootfs_overlay"
+BR2_ROOTFS_POST_BUILD_SCRIPT="board/canaan/k210-soc/post-build.sh"
+BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
+BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/canaan/k210-soc/genimage.cfg"
+
+# Bootloader and related host tools
+BR2_TARGET_UBOOT=y
+BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2022.04"
+BR2_TARGET_UBOOT_CONFIG_FRAGMENT_FILES="board/canaan/k210-soc/uboot.config"
+BR2_TARGET_UBOOT_BOARD_DEFCONFIG="sipeed_maix_bitm"
+BR2_TARGET_UBOOT_FORMAT_BIN=y
+BR2_PACKAGE_HOST_UBOOT_TOOLS=y
+BR2_PACKAGE_HOST_GENIMAGE=y
+BR2_PACKAGE_HOST_DOSFSTOOLS=y
+BR2_PACKAGE_HOST_MTOOLS=y
+BR2_PACKAGE_HOST_PYTHON_KFLASH=y