9.13. riscv (RISC-V)

9.13.1. riscv

Each variant in this first group corresponds to a GCC multilib option with different RISC-V standard extensions.

  • rv32i

  • rv32iac

  • rv32im

  • rv32imac

  • rv32imafc

  • rv32imafd

  • rv32imafdc

  • rv64imac

  • rv64imafd

  • rv64imafdc

Each variant reflects an ISA with ABI and code model choice. All rv64 BSPs have medany code model by default, while rv32 BSPs are medlow. The reason is that RV32 medlow can access the entire 32-bit address space, while RV64 medlow can only access addresses below 0x80000000. With RV64 medany, it’s possible to perform accesses above 0x80000000. The BSP must be started in machine mode.

The reference platforms for the rv* variants include the QEMU virt and spike machines and the Spike RISC-V ISA simulator.

The BSP also provides the following variants for specific hardware targets:

  • frdme310arty - The reference platform for this variant is the Arty FPGA board with the SiFive Freedom E310 reference design.

  • mpfs64imafdc - The reference platform for this variant is the Microchip PolarFire SoC Icicle Kit.

  • kendrytek210 - The reference platform for this variant is the Kendryte K210 SoC on the Sipeed MAiX BiT or Maixduino board.

9.13.1.1. Build Configuration Options

The following options can be used in the BSP section of the waf configuration INI file. The waf defaults can be used to inspect the values.

BSP_PRESS_KEY_FOR_RESET

If defined to a non-zero value, then print a message and wait until pressed before resetting board when application terminates.

BSP_RESET_BOARD_AT_EXIT

If defined to a non-zero value, then reset the board when the application terminates.

BSP_PRINT_EXCEPTION_CONTEXT

If defined to a non-zero value, then print the exception context when an unexpected exception occurs.

BSP_FDT_BLOB_SIZE_MAX

The maximum size of the device tree blob in bytes (default is 65536).

BSP_DTB_IS_SUPPORTED

If defined to a non-zero value, then the device tree blob is embedded in the BSP.

BSP_DTB_HEADER_PATH

The path to the header file containing the device tree blob.

BSP_CONSOLE_BAUD

The default baud for console driver devices (default is 115200).

RISCV_MAXIMUM_EXTERNAL_INTERRUPTS

The maximum number of external interrupts supported by the BSP (default is 64).

RISCV_ENABLE_HTIF_SUPPORT

Enable the Host/Target Interface (HTIF) support (enabled by default).

RISCV_CONSOLE_MAX_NS16550_DEVICES

The maximum number of NS16550 devices supported by the console driver (default is 2).

RISCV_ENABLE_SIFIVE_UART_SUPPORT

Enable the SiFive console UART (disabled by default).

RISCV_RAM_REGION_BEGIN

The begin of the RAM region for linker command file (default is 0x80000000).

RISCV_RAM_REGION_SIZE

The size of the RAM region for linker command file (default 64MiB).

RISCV_ENABLE_FRDME310ARTY_SUPPORT

Enables support sifive Freedom E310 Arty board if defined to a non-zero value,otherwise it is disabled (disabled by default).

RISCV_ENABLE_MPFS_SUPPORT

Enables support Microchip PolarFire SoC if defined to a non-zero value, otherwise it is disabled (disabled by default).

RISCV_ENABLE_KENDRYTE_K210_SUPPORT

Enables support for the Kendtryte K210 SoC if defined to a non-zero value, otherwise it is disabled (disabled by default).

RISCV_BOOT_HARTID

The boot hartid (processor number) of risc-v cpu by default 0.

9.13.1.2. Interrupt Controller

Exactly one Core Local Interruptor (CLINT) and exactly one Platform-Level Interrupt Controller (PLIC) are supported. The maximum number of external interrupts supported by the BSP is defined by the RISCV_MAXIMUM_EXTERNAL_INTERRUPTS BSP option.

9.13.1.3. Clock Driver

The clock driver uses the CLINT timer.

9.13.1.4. Console Driver

The console driver supports devices compatible to:

  • “ucb,htif0” (depending on the RISCV_ENABLE_HTIF_SUPPORT BSP option),

  • “ns16550a” (see RISCV_CONSOLE_MAX_NS16550_DEVICES BSP option),

  • “ns16750” (see RISCV_CONSOLE_MAX_NS16550_DEVICES BSP option), and

  • “sifive,uart0” (see RISCV_ENABLE_SIFIVE_UART_SUPPORT BSP option).

They are initialized according to the device tree. The console driver does not configure the pins or peripheral clocks. The console device is selected according to the device tree “/chosen/stdout-path” property value.

9.13.1.5. QEMU

All of the BSP variants that start with rv can be run on QEMU’s virt and spike machines. For instance, to run the rv64imafdc BSP with the following “config.ini” file.

[riscv/rv64imafdc]

Run the following QEMU command.

$ qemu-system-riscv64 -M virt -nographic -bios $RTEMS_EXE
$ qemu-system-riscv64 -M spike -nographic -bios $RTEMS_EXE

9.13.1.6. Spike

All of the BSP variants that start with rv can be run on Spike. For instance, to run the rv64imafdc BSP with the following “config.ini” file.

[riscv/rv64imafdc]

Run the following Spike command.

$ spike --isa=rv64imafdc $RTEMS_EXE

Unlike QEMU, Spike supports enabling/disabling a subset of the imafdc extensions and has support for further RISC-V extensions as well. A fault will be triggered if an executable built with rv64imafdc RISC-V’s -march option run on Spike with –isa=rv64i option. If no –isa option is specified, the default is rv64imafdc.

9.13.1.7. Microchip PolarFire SoC

The PolarFire SoC is the 4x 64-bit RISC-V U54 cores and a 64-bit RISC-V E51 monitor core SoC from the Microchip.

The mpfs64imafdc BSP variant supports the U54 cores but not the E51 because the E51 monitor core is reserved for the first stage bootloader (Hart Software Services). In order to boot from the first U54 core, RISCV_BOOT_HARTID is set to 1 by default.

The device tree blob is embedded in the mpfs64imafdc BSP variant by default with the BSP_DTB_IS_SUPPORTED enabled and the DTB header path BSP_DTB_HEADER_PATH is set to bsp/mpfs-dtb.h.

SMP test procedure for the Microchip PolarFire Icicle Kit:

The “config.ini” file.

[riscv/mpfs64imafdc]
BUILD_TESTS = True
RTEMS_POSIX_API=True
RTEMS_SMP = True
BSP_START_COPY_FDT_FROM_U_BOOT=False
BSP_VERBOSE_FATAL_EXTENSION = False

Build RTEMS.

$ ./waf configure --prefix=$HOME/rtems-start/rtems/6
$ ./waf

Convert .exe to .elf file.

$ riscv-rtems6-objcopy build/riscv/mpfs64imafdc/testsuites/smptests/smp01.exe build/riscv/mpfs64imafdc/testsuites/smptests/smp01.elf

Generate a payload for the smp01.elf using the hss-payload-generator.

  • Copy smp01.elf file to the HSS/tools/hss-payload-generator/test directory.

  • Go to hss-payload-generator source directory.

$ cd hart-software-services/tools/hss-payload-generator

  • Edit test/uboot.yaml file for the hart entry points and correct name of the binary file.

set-name: 'PolarFire-SoC-HSS::RTEMS'
hart-entry-points: {u54_1: '0x1000000000', u54_2: '0x1000000000', u54_3: '0x1000000000', u54_4: '0x1000000000'}
payloads:
 test/smp01.elf: {exec-addr: '0x1000000000', owner-hart: u54_1, secondary-hart: u54_2, secondary-hart: u54_3, secondary-hart: u54_4, priv-mode: prv_m, skip-opensbi: true}

  • Generate payload

$ ./hss-payload-generator -c test/uboot.yaml payload.bin

Once the payload binary is generated, it should be copied to the eMMC/SD.

FPGA design with HSS programming file.

Program the eMMC/SD with the payload binary.

  • Power Cycle the Microchip PolarFire Icicle Kit and stop at the HSS.

  • type “mmc” and then “usbdmsc” on the HSS terminal(UART0).

  • Load the payload.bin from the Host PC.

$ sudo dd if=payload.bin of=/dev/sdb bs=512

Reset the Microchip PolarFire SoC Icicle Kit.

Serial terminal UART1 displays the SMP example messages

*** BEGIN OF TEST SMP 1 ***
*** TEST VERSION: 6.0.0.ef33f861e16de9bf4190a36e4d18062c7300986c
*** TEST STATE: EXPECTED_PASS
*** TEST BUILD: RTEMS_POSIX_API RTEMS_SMP
*** TEST TOOLS: 12.1.1 20220622 (RTEMS 6, RSB 3cb78b0b815ba05d17f5c6
            5865d246a8333aa087, Newlib ea99f21)

CPU 3 start task TA0
CPU 2 running Task TA0
CPU 3 start task TA1
CPU 1 running Task TA1
CPU 3 start task TA2
CPU 0 running Task TA2

*** END OF TEST SMP 1 ***

9.13.1.8. Kendryte K210

The Kendryte K210 SoC is a dual core 64-bit RISC-V SoC with an AI NPU, built in SRAM, and a variety of peripherals. Currently just the console UART, interrupt controller, and timer are supported.

The device tree blob is embedded in the kendrytek210 BSP variant by default. When the kendrytek210 BSP variant is selected, BSP_DTB_IS_SUPPORTED enabled and the DTB header path BSP_DTB_HEADER_PATH is set to bsp/kendryte-k210-dtb.h.

The kendrytek210 BSP variant has been tested on the following simulator and boards:

  • Renode.io simulator using the Kendrtye k210 model

  • Sipeed MAiX BiT board

  • Sipeed Maixduino board

  • Sipeed MAiX Dock board

Building the Kendryte K210 BSP

Configuration file config.ini:

[riscv/kendrytek210]
RTEMS_SMP = True

Build RTEMS:

$ ./waf configure --prefix=$HOME/rtems-start/rtems/6
$ ./waf

Flash an executable to a supported K210 board

Binary images can be flashed to the Sipeed boards through the USB port using the kflash.py utility available from the python pip utility.

$ riscv-rtems6-objcopy -Obinary ticker.exe ticker.bin
$ kflash.py --uart /dev/ttyUSB0 ticker.bin

After the image is flashed, the RTEMS image will automatically boot. It will also run when the board is reset or powered through the USB cable. The USB port provides the power and console UART. Plug the USB cable into a host PC and bring up a terminal emulator at 115200 baud, 8 data bits, 1 stop bit, no parity, and no flow control. On Linux the UART device is often /dev/ttyUSB0.

Run a RTEMS application on the Renode.io simulator

RTEMS executables compiled with the kendrytek210 BSP can run on the renode.io simulator using the built-in K210 model. The simulator currently supports the console UART, interrupt controller, and timer.

To install renode.io please refer to the installation instructions. Once installed, save the following file as k210_rtems.resc.

using sysbus

$bin?=@ticker.exe

mach create "K210"

machine LoadPlatformDescription @platforms/cpus/kendryte_k210.repl

showAnalyzer uart

sysbus Tag <0x50440000 0x10000> "SYSCTL"
sysbus Tag <0x50440018 0x4> "pll_lock" 0xFFFFFFFF
sysbus Tag <0x5044000C 0x4> "pll1"
sysbus Tag <0x50440008 0x4> "pll0"
sysbus Tag <0x50440020 0x4> "clk_sel0"
sysbus Tag <0x50440028 0x4> "clk_en_cent"
sysbus Tag <0x5044002c 0x4> "clk_en_peri"

macro reset
"""
   sysbus LoadELF $bin
"""
runMacro $reset

After saving the above file in in the same directory as your RTEMS ELF images, start renode and load the k210_rtems.resc script to start the emulation.

(monitor) s @k210_rtems.resc

You should see a renode UART window and the RTEMS ticker example output. If you want to run a different RTEMS image, you can edit the file or enter the following on the renode console.

(monitor) $bin=@smp08.exe
(monitor) s @k210_rtems.resc

The above example will run the SMP08 example instead of ticker.

Generating the Device Tree Header

The kendrytek210 BSP uses a built in device tree blob. If additional peripheral support is added to the BSP, the device tree may need to be updated. After editing the device tree source, compile it to a device tree blob with the following command:

$ dtc -O dtb -b 0 -o kendryte-k210.dtb kendryte-k210.dts

The dtb file can then be converted to a C array using the rtems-bin2c tool. The data for the device tree binary can then replace the existing device tree binary data in the kendryte-k210-dtb.h header file.

9.13.2. noel

This BSP supports the NOEL-V systems from Cobham Gaisler. The NOEL-V is a synthesizable VHDL model of a processor that implements the RISC-V architecture. It is part of the open source GRLIB IP Library. The following BSP variants correspond to common NOEL-V configurations:

  • noel32im

  • noel32imafd

  • noel64imac

  • noel64imafd

  • noel64imafdc

The start of the memory is set to 0x0 to match a standard NOEL-V system, but can be changed using the RISCV_RAM_REGION_BEGIN configuration option. The size of the memory is taken from the information available in the device tree.

9.13.2.1. Reference Designs

The BSP has been tested with NOEL-V reference designs for Digilent Arty A7, Microchip PolarFire Splash Kit, and Xilinx KCU105. See the accompanying quickstart guide for each reference design to determine which BSP configuration to use.

9.13.2.2. Build Configuration Options

The following options can be used in the BSP section of the waf configuration INI file. The waf defaults can be used to inspect the values.

BSP_CONSOLE_USE_INTERRUPTS

Use the Termios interrupt mode in the console driver (true by default).

BSP_FDT_BLOB_SIZE_MAX

The maximum size of the device tree blob in bytes (262144 by default).

RISCV_CONSOLE_MAX_APBUART_DEVICES

The maximum number of APBUART devices supported by the console driver (2 by default).

RISCV_RAM_REGION_BEGIN

The begin of the RAM region for linker command file (0x0 by default).

RISCV_MAXIMUM_EXTERNAL_INTERRUPTS

The maximum number of external interrupts supported by the BSP (64 by default).

9.13.3. griscv

This RISC-V BSP supports chips using the GRLIB.