BSP Supporting QEMU's PReP Emulation
As of rtems-4.11 two variants of the 'motorola_powerpc' BSP family are available:
The most significant differences between the emulation and real PREP hardware are
- no OpenPIC, just a 8259 PIC (even though qemu implements an openpic at least to some extent it is not configured into the prep platform as of qemu-0.14.1).
- no VME (absense of the VME controller is detected by the BSP)
- the only network chip supported by both, qemu and vanilla RTEMS is the ISA NE2000 controller. Note that the default interrupt line settings used by RTEMS and QEMU differ: RTEMS uses 5 and QEMU 9. This can be addressed by passing a RTEMS commandline option --ne2k-irq=9. Other controllers (i8559, e1000, pcnet) implemented by qemu can also be used but require unbundled RTEMS drivers (libbsdport). Note that the bundled 'if_fxp' has not been ported to PPC and works on x86 only.
- unlike a real motorola board you can run qemu emulating a 7400 CPU which features altivec. I.e., you can use this BSP (altivec-enabled variant) to test altivec-enabled code.
qemu had quite a few bugs related to the PREP platform. Version 0.12.4, for example, required patches. 0.14.1 seems to have fixed the show-stoppers. Hence, you need at least qemu-0.14.1 for this BSP; it should work without the need for patching QEMU.
qemu requires you to use a BIOS/firmware. The one that came with qemu 0.12.4 didn't work for me so I created a minimal dummy that provides enough functionality for the RTEMS bootloader to work.
You can compile the BSP for either a 604 CPU or a 7400 (altivec-enabled). Note that you cannot run the altivec-enabled BSP variant on a CPU w/o altivec/SIMD hardware. The non-altivec variant is called 'qemuprep' and the altivec-enabled one 'qemuprep-altivec'. Hence, you can configure RTEMS:
604/non-altivec variant only: configure --target=powerpc-rtems --enable-rtemsbsp=qemuprep 7400/altivec variant only: configure --target=powerpc-rtems --enable-rtemsbsp=qemuprep-altivec both variants: configure --target=powerpc-rtems --enable-rtemsbsp='qemuprep qemuprep-altivec'
In case you have no pre-built qemu-0.14.1 you can compile it yourself:
cd qemu-0.14.1 configure --target-list=ppc-softmmu make
A number of command-line options are important (BTW: make sure you run the PPC/PREP emulator and not a natively installed i386/PC emulating 'qemu')
-M prep --- select machine type: prep -cpu 604 --- select 604 CPU for non-altivec variant -cpu 7400 --- select 7400 CPU for altivec variant NOTE: the 7455 and 7457 emulations are buggy as of qemu-0.14.1 and they won't work. -bios <rtems-install-prefix>/powerpc-rtems/qemuprep/qemu_fakerom.bin -bios <rtems-install-prefix>/powerpc-rtems/qemuprep-altivec/qemu_fakerom.bin --- select proprietary dummy 'BIOS' -nographic --- redirect serial/IO to console where qemu is run -kernel <path> --- path to your RTEMS executable (.ralf file, e.g., 'hello.ralf') -no-reboot --- terminate after one run -append <arg> --- RTEMS kernel comand line (use e.g., to modify ne2000 driver interrupt line)
(We assume your RTEMS application is correctly configured and built for networking using the ne2k adapter [other adapters can be used with unbundled/libbsdport drivers])
I use networking with a 'tap' interface on the host machine and can then communicate with the emulated target in any desired way.
On (linux) host:
# create a 'permanent' tap device that can be used by myself # (as non-root user). sudo tunctl -u `id -u` # configure tap0 interface sudo ifconfig tap0 10.1.1.1 netmask 255.255.255.0 up # provide a suitable dhcpd config file (for the emulated # platform to boot: IP address etc. # # execute dhcp on host sudo dhcpd -d tap0
Start emulated prep platform:
ppc-softmmu/qemu-system-ppc \ -M prep \ -cpu 7400 \ -bios <rtems-prefix>/powerpc-rtems/qemuprep-altivec/lib/qemu_fakerom.bin \ -kernel <my_path>/my_app.ralf \ -append --ne2k-irq=9 \ -nographic \ -no-reboot \ -net nic,model=ne2k_isa \ -net tap,vlan=0,ifname=tap0,script=no,downscript=no
Again: if you use the non-altivec BSP variant, use -cpu 604 and if you use the altivec-enabled variant then you MUST use -cpu 7400.