Microchip PolarFire SoC Icicle Kit (microchip-icicle-kit)

Microchip PolarFire SoC Icicle Kit integrates a PolarFire SoC, with one SiFive’s E51 plus four U54 cores and many on-chip peripherals and an FPGA.

For more details about Microchip PolarFire SoC, please see: https://www.microsemi.com/product-directory/soc-fpgas/5498-polarfire-soc-fpga

The Icicle Kit board information can be found here: https://www.microsemi.com/existing-parts/parts/152514

Supported devices

The microchip-icicle-kit machine supports the following devices:

  • 1 E51 core
  • 4 U54 cores
  • Core Level Interruptor (CLINT)
  • Platform-Level Interrupt Controller (PLIC)
  • L2 Loosely Integrated Memory (L2-LIM)
  • DDR memory controller
  • 5 MMUARTs
  • 1 DMA controller
  • 2 GEM Ethernet controllers
  • 1 SDHC storage controller

Boot options

The microchip-icicle-kit machine can start using the standard -bios functionality for loading its BIOS image, aka Hart Software Services (HSS). HSS loads the second stage bootloader U-Boot from an SD card. Then a kernel can be loaded from U-Boot. It also supports direct kernel booting via the -kernel option along with the device tree blob via -dtb. When direct kernel boot is used, the OpenSBI fw_dynamic BIOS image is used to boot a payload like U-Boot or OS kernel directly.

The user provided DTB should have the following requirements:

  • The /cpus node should contain at least one subnode for E51 and the number of subnodes should match QEMU’s -smp option
  • The /memory reg size should match QEMU’s selected ram_size via -m
  • Should contain a node for the CLINT device with a compatible string “riscv,clint0”

QEMU follows below truth table to select which payload to execute:

-bios -kernel -dtb payload
N N don’t care HSS
Y don’t care don’t care HSS
N Y Y kernel

The memory is set to 1537 MiB by default which is the minimum required high memory size by HSS. A sanity check on ram size is performed in the machine init routine to prompt user to increase the RAM size to > 1537 MiB when less than 1537 MiB ram is detected.

Running HSS

HSS 2020.12 release is tested at the time of writing. To build an HSS image that can be booted by the microchip-icicle-kit machine, type the following in the HSS source tree:

$ export CROSS_COMPILE=riscv64-linux-
$ cp boards/mpfs-icicle-kit-es/def_config .config
$ make BOARD=mpfs-icicle-kit-es

Download the official SD card image released by Microchip and prepare it for QEMU usage:

$ wget ftp://ftpsoc.microsemi.com/outgoing/core-image-minimal-dev-icicle-kit-es-sd-20201009141623.rootfs.wic.gz
$ gunzip core-image-minimal-dev-icicle-kit-es-sd-20201009141623.rootfs.wic.gz
$ qemu-img resize core-image-minimal-dev-icicle-kit-es-sd-20201009141623.rootfs.wic 4G

Then we can boot the machine by:

$ qemu-system-riscv64 -M microchip-icicle-kit -smp 5 \
    -bios path/to/hss.bin -sd path/to/sdcard.img \
    -nic user,model=cadence_gem \
    -nic tap,ifname=tap,model=cadence_gem,script=no \
    -display none -serial stdio \
    -chardev socket,id=serial1,path=serial1.sock,server=on,wait=on \
    -serial chardev:serial1

With above command line, current terminal session will be used for the first serial port. Open another terminal window, and use minicom to connect the second serial port.

$ minicom -D unix\#serial1.sock

HSS output is on the first serial port (stdio) and U-Boot outputs on the second serial port. U-Boot will automatically load the Linux kernel from the SD card image.

Direct Kernel Boot

Sometimes we just want to test booting a new kernel, and transforming the kernel image to the format required by the HSS bootflow is tedious. We can use ‘-kernel’ for direct kernel booting just like other RISC-V machines do.

In this mode, the OpenSBI fw_dynamic BIOS image for ‘generic’ platform is used to boot an S-mode payload like U-Boot or OS kernel directly.

For example, the following commands show building a U-Boot image from U-Boot mainline v2021.07 for the Microchip Icicle Kit board:

$ export CROSS_COMPILE=riscv64-linux-
$ make microchip_mpfs_icicle_defconfig

Then we can boot the machine by:

$ qemu-system-riscv64 -M microchip-icicle-kit -smp 5 -m 2G \
    -sd path/to/sdcard.img \
    -nic user,model=cadence_gem \
    -nic tap,ifname=tap,model=cadence_gem,script=no \
    -display none -serial stdio \
    -kernel path/to/u-boot/build/dir/u-boot.bin \
    -dtb path/to/u-boot/build/dir/u-boot.dtb


  • Check the “stdout-path” property in the /chosen node in the DTB to determine which serial port is used for the serial console, e.g.: if the console is set to the second serial port, change to use “-serial null -serial stdio”.
  • The default U-Boot configuration uses CONFIG_OF_SEPARATE hence the ELF image u-boot cannot be passed to “-kernel” as it does not contain the DTB hence u-boot.bin has to be used which does contain one. To use the ELF image, we need to change to CONFIG_OF_EMBED or CONFIG_OF_PRIOR_STAGE.