Nuttx Guide

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qemu-armv7a ​

This board configuration will use QEMU to emulate generic ARM v7-A series hardware platform and provides support for these devices:

  • GICv2 interrupt controllers
  • ARM Generic Timer
  • PL011 UART controller
  • PCI ECAM
  • VirtIO Device

Getting Started ​

NSH (Single Core) ​

Configuring NuttX and compile:

 ./tools/configure.sh -l qemu-armv7a:nsh
 make

Running with qemu:

 qemu-system-arm -cpu cortex-a7 -nographic \
-machine virt,virtualization=off,gic-version=2 \
-net none -chardev stdio,id=con,mux=on -serial chardev:con \
-mon chardev=con,mode=readline -kernel ./nuttx

KNSH (Single Core) ​

This is a configuration of testing the BUILD_KERNEL configuration:

 cd nuttx
 ./tools/configure.sh qemu-armv7a:knsh
 make V=1 -j7
 make export V=1
 cd ../apps
 ./tools/mkimport.sh -z -x ../nuttx/nuttx-export-*.tar.gz
 make import V=1
 cd ../nuttx
 qemu-system-arm -semihosting -M virt -m 1024 -nographic -kernel ./nuttx

NuttShell (NSH) NuttX-12.3.0-RC0
nsh> uname -a
NuttX 12.3.0-RC0 28dee592a3-dirty Oct 12 2023 03:03:07 arm qemu-armv7a
nsh> ps
  PID GROUP PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK           STACK   USED  FILLED COMMAND
    0     0   0 FIFO     Kthread N-- Ready              0000000000000000 004088 000896  21.9%  Idle_Task
    1     1 100 RR       Kthread --- Waiting  Semaphore 0000000000000000 004040 000304   7.5%  lpwork 0x40119398 0x401193ac
    2     2 100 RR       Task    --- Running            0000000000000000 003032 001032  34.0%  /system/bin/init
nsh> free
                   total       used       free    largest  nused  nfree
        Kmem:  133058556      16644  133041912  133041152     41      3
        Page:  134217728    1105920  133111808  133111808
nsh> /system/bin/hello
Hello, World!!
nsh>

Inter-VM share memory Device (ivshmem) ​

Inter-VM shared memory support support can be found in drivers/pci/pci_ivshmem.c.

This implementation is for ivshmem-v1 which is compatible with QEMU and ACRN hypervisor but won't work with Jailhouse hypervisor which uses ivshmem-v2.

Please refer to the official Qemu ivshmem documentation for more information.

This is an example implementation for OpenAMP based on the Inter-VM share memory(ivshmem):

rpproxy_ivshmem:  Remote slave(client) proxy process.
rpserver_ivshmem: Remote master(host) server process.

Steps for Using NuttX as IVSHMEM host and guest

  1. Build images

a. Build rpserver_ivshmem:

     cmake -B server -DBOARD_CONFIG=qemu-armv7a:rpserver_ivshmem -GNinja
     cmake --build server

b. Build rpproxy_ivshmem:

     cmake -B proxy -DBOARD_CONFIG=qemu-armv7a:rpproxy_ivshmem -GNinja
     cmake --build proxy
  1. Bringup firmware via Qemu:

The Inter-VM Shared Memory device basic syntax is:

-device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,addr=0xb \
-object memory-backend-file,id=shmmem-shmem0,mem-path=/dev/shm/ivshmem0,size=4194304,share=yes

a. Start rpserver_ivshmem:

     qemu-system-arm -cpu cortex-a7 -nographic -machine virt,highmem=off \
      -object memory-backend-file,id=shmmem-shmem0,mem-path=/dev/shm/ivshmem0,size=4194304,share=yes \
      -device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,addr=0xb \
      -kernel server/nuttx -nographic

b. Start rpproxy_ivshmem:

     qemu-system-arm -cpu cortex-a7 -nographic -machine virt,highmem=off \
      -object memory-backend-file,discard-data=on,id=shmmem-shmem0,mem-path=/dev/shm/ivshmem0,size=4194304,share=yes \
      -device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,addr=0xb \
      -kernel proxy/nuttx -nographic

c. Check the RPMSG Syslog in rpserver shell:

In the current configuration, the proxy syslog will be sent to the server by default. You can check whether there is proxy startup log in the server shell.

RpServer bring up:

 qemu-system-arm -cpu cortex-a7 -nographic -machine virt,highmem=off \
  -object memory-backend-file,id=shmmem-shmem0,mem-path=/dev/shm/ivshmem0,size=4194304,share=yes \
  -device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,addr=0xb \
  -kernel server/nuttx -nographic
[    0.000000] [ 0] [  INFO] [server] pci_register_rptun_ivshmem_driver: Register ivshmem driver, id=0, cpuname=proxy, master=0
...
[    0.306127] [ 3] [  INFO] [server] rptun_ivshmem_probe: Start the wdog

After rpproxy bring up, check the log from rpserver:

NuttShell (NSH) NuttX-10.4.0
server>
[    0.000000] [ 0] [  INFO] [proxy] pci_register_rptun_ivshmem_driver: Register ivshmem driver, id=0, cpuname=server, master=1
...
[    0.314039] [ 3] [  INFO] [proxy] ivshmem_probe: shmem addr=0x10400000 size=4194304 reg=0x10008000

d. IPC test via RPMSG socket:

Start rpmsg socket server:

server> rpsock_server stream block test
server: create socket SOCK_STREAM nonblock 0
server: bind cpu , name test ...
server: listen ...
server: try accept ...
server: Connection accepted -- 4
server: try accept ...

Switch to proxy shell and start rpmsg socket client, test start:

proxy> rpsock_client stream block test server
client: create socket SOCK_STREAM nonblock 0
client: Connecting to server,test...
client: Connected
client send data, cnt 0, total len 64, BUFHEAD process0007, msg0000, name:test
client recv data process0007, msg0000, name:test
...
client recv done, total 4096000, endflags, send total 4096000
client: Terminating

Check the log on rpserver shell:

server recv data normal exit
server Complete ret 0, errno 0

Debugging with QEMU ​

The nuttx ELF image can be debugged with QEMU.

  1. To debug the nuttx (ELF) with symbols, make sure the following change have applied to defconfig:

    +CONFIG_DEBUG_SYMBOLS=y

  2. Run QEMU (Single Core) at shell terminal 1:

     qemu-system-arm -cpu cortex-a7 -nographic \
-machine virt,virtualization=off,gic-version=2 \
-net none -chardev stdio,id=con,mux=on -serial chardev:con \
-mon chardev=con,mode=readline -kernel ./nuttx -S -s

  3. Run gdb with TUI, connect to QEMU, load nuttx and continue (at shell terminal 2):

     arm-none-eabi-gdb -tui --eval-command='target remote localhost:1234' nuttx
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
nx_start () at armv7-a/arm_head.S:209
(gdb)

PCI support ​

To enable PCI support, set the following options:

CONFIG_DEVICE_TREE=y
CONFIG_PCI=y
CONFIG_PCI=y

Then run qemu with:

-machine virt,highmem=off,virtualization=off,gic-version=2

The command that starts QEMU and enables the QEMU EDU device looks like this:

qemu-system-arm -cpu cortex-a7 -nographic \
-machine virt,highmem=off,virtualization=off,gic-version=2 \
-chardev stdio,id=con,mux=on -serial chardev:con -mon chardev=con,mode=readline \
-kernel nuttx -device edu