alexghiti.github.io

riscv XIP kernel

At the moment, it was only tested on Microchip Polarfire SoC.

Quick way

1. Download SD card image from https://github.com/polarfire-soc/meta-polarfire-soc-yocto-bsp/releases

    $ wget https://github.com/polarfire-soc/meta-polarfire-soc-yocto-bsp/releases/download/v2021.02/core-image-minimal-dev-icicle-kit-es-sd-20210216171231.rootfs.wic.gz
   

2. Hart Software Services

   Follow instructions here https://github.com/polarfire-soc/hart-software-services#building (you can use .config based on 0.99.15 as I had some issues building it).

3. Linux kernel

   Build using the config here: .config

   This can be derived from defconfig by using the following command:

    $ tuxmake --verbose --build-dir riscv_rv64_xipkernel --directory /home/alex/wip/linux --target-arch riscv --kconfig defconfig config --kconfig-add CONFIG_DEBUG_KERNEL=y --kconfig-add CONFIG_DEBUG_INFO=y --kconfig-add CONFIG_GDB_SCRIPTS=y --kconfig-add CONFIG_PCI=n --kconfig-add CONFIG_SPARSEMEM_MANUAL=y --kconfig-add CONFIG_DEBUG_VM_PGTABLE=n --kconfig-add CONFIG_XIP_KERNEL=y
   
   

4. Launching using qemu

   Support for Polarfire in qemu is recent, more instructions can be found here: qemu Polarfire

   Use the following command line (adapting the path):

    $ qemu-system-riscv64                                               					\
        -M microchip-icicle-kit                                         					\
        -bios hart-software-services/Default/hss.bin                                				\
        -smp 5 -display none -nic user,model=cadence_gem -serial null                       			\
        -chardev socket,id=serial1,path=/tmp/serial1.sock,server -serial chardev:serial1            		\
        -drive if=sd,format=raw,file=core-image-minimal-dev-icicle-kit-es-sd-20210216171231.rootfs.wic.gz   	\
        -device loader,addr=0x21000000,file=arch/riscv/boot/xipImage                        			\
        -m 6G -D qemu.log -monitor stdio -s
   

   Launch the following to connect to the serial output:

    $ sudo minicom -D unix#/tmp/serial1.sock
   

   In uboot console, launch the XIP kernel using the following command:

    RISC-V # go 0x21000000
   

   And in parallel, you can launch gdb using the following gdb commands:

    (gdb) target extended-remote :1234
    (gdb) add-inferior
    (gdb) inferior 2
    (gdb) attach 2
    (gdb) set schedule-multiple
    (gdb) info threads
   

   Generally I don’t have any output in minicom from the kernel (I have not found why yet). But I can see kernel messages by compiling the kernel with following config:

    CONFIG_DEBUG_INFO=y
    CONFIG_GDB_SCRIPTS=y
   

   And by using the following command in gdb:

    (gdb) file vmlinux
    (gdb) lx-dmesg
   

Long way (never tested)

See https://github.com/polarfire-soc/polarfire-soc-buildroot-sdk