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ppce500 generic platform (``ppce500``)
======================================
QEMU for PPC supports a special ``ppce500`` machine designed for emulation and
virtualization purposes.
Supported devices
-----------------
The ``ppce500`` machine supports the following devices:
* PowerPC e500 series core (e500v2/e500mc/e5500/e6500)
* Configuration, Control, and Status Register (CCSR)
* Multicore Programmable Interrupt Controller (MPIC) with MSI support
* 1 16550A UART device
* 1 Freescale MPC8xxx I2C controller
* 1 Pericom pt7c4338 RTC via I2C
* 1 Freescale MPC8xxx GPIO controller
* Power-off functionality via one GPIO pin
* 1 Freescale MPC8xxx PCI host controller
* VirtIO devices via PCI bus
* 1 Freescale Enhanced Triple Speed Ethernet controller (eTSEC)
Hardware configuration information
----------------------------------
The ``ppce500`` machine automatically generates a device tree blob ("dtb")
which it passes to the guest, if there is no ``-dtb`` option. This provides
information about the addresses, interrupt lines and other configuration of
the various devices in the system.
If users want to provide their own DTB, they can use the ``-dtb`` option.
These DTBs should have the following requirements:
* The number of subnodes under /cpus node should match QEMU's ``-smp`` option
* The /memory reg size should match QEMU’s selected ram_size via ``-m``
Both ``qemu-system-ppc`` and ``qemu-system-ppc64`` provide emulation for the
following 32-bit PowerPC CPUs:
* e500v2
* e500mc
Additionally ``qemu-system-ppc64`` provides support for the following 64-bit
PowerPC CPUs:
* e5500
* e6500
The CPU type can be specified via the ``-cpu`` command line. If not specified,
it creates a machine with e500v2 core. The following example shows an e6500
based machine creation:
.. code-block:: bash
$ qemu-system-ppc64 -nographic -M ppce500 -cpu e6500
Boot options
------------
The ``ppce500`` machine can start using the standard -kernel functionality
for loading a payload like an OS kernel (e.g.: Linux), or U-Boot firmware.
When -bios is omitted, the default pc-bios/u-boot.e500 firmware image is used
as the BIOS. QEMU follows below truth table to select which payload to execute:
===== ========== =======
-bios -kernel payload
===== ========== =======
N N u-boot
N Y kernel
Y don't care u-boot
===== ========== =======
When both -bios and -kernel are present, QEMU loads U-Boot and U-Boot in turns
automatically loads the kernel image specified by the -kernel parameter via
U-Boot's built-in "bootm" command, hence a legacy uImage format is required in
such scenario.
Running Linux kernel
--------------------
Linux mainline v5.11 release is tested at the time of writing. To build a
Linux mainline kernel that can be booted by the ``ppce500`` machine in
64-bit mode, simply configure the kernel using the defconfig configuration:
.. code-block:: bash
$ export ARCH=powerpc
$ export CROSS_COMPILE=powerpc-linux-
$ make corenet64_smp_defconfig
$ make menuconfig
then manually select the following configuration:
Platform support > Freescale Book-E Machine Type > QEMU generic e500 platform
To boot the newly built Linux kernel in QEMU with the ``ppce500`` machine:
.. code-block:: bash
$ qemu-system-ppc64 -M ppce500 -cpu e5500 -smp 4 -m 2G \
-display none -serial stdio \
-kernel vmlinux \
-initrd /path/to/rootfs.cpio \
-append "root=/dev/ram"
To build a Linux mainline kernel that can be booted by the ``ppce500`` machine
in 32-bit mode, use the same 64-bit configuration steps except the defconfig
file should use corenet32_smp_defconfig.
To boot the 32-bit Linux kernel:
.. code-block:: bash
$ qemu-system-ppc64 -M ppce500 -cpu e500mc -smp 4 -m 2G \
-display none -serial stdio \
-kernel vmlinux \
-initrd /path/to/rootfs.cpio \
-append "root=/dev/ram"
Running U-Boot
--------------
U-Boot mainline v2021.07 release is tested at the time of writing. To build a
U-Boot mainline bootloader that can be booted by the ``ppce500`` machine, use
the qemu-ppce500_defconfig with similar commands as described above for Linux:
.. code-block:: bash
$ export CROSS_COMPILE=powerpc-linux-
$ make qemu-ppce500_defconfig
You will get u-boot file in the build tree.
When U-Boot boots, you will notice the following if using with ``-cpu e6500``:
.. code-block:: none
CPU: Unknown, Version: 0.0, (0x00000000)
Core: e6500, Version: 2.0, (0x80400020)
This is because we only specified a core name to QEMU and it does not have a
meaningful SVR value which represents an actual SoC that integrates such core.
You can specify a real world SoC device that QEMU has built-in support but all
these SoCs are e500v2 based MPC85xx series, hence you cannot test anything
built for P4080 (e500mc), P5020 (e5500) and T2080 (e6500).
Networking
----------
By default a VirtIO standard PCI networking device is connected as an ethernet
interface at PCI address 0.1.0, but we can switch that to an e1000 NIC by:
.. code-block:: bash
$ qemu-system-ppc64 -M ppce500 -smp 4 -m 2G \
-display none -serial stdio \
-bios u-boot \
-nic tap,ifname=tap0,script=no,downscript=no,model=e1000
The QEMU ``ppce500`` machine can also dynamically instantiate an eTSEC device
if “-device eTSEC” is given to QEMU:
.. code-block:: bash
-netdev tap,ifname=tap0,script=no,downscript=no,id=net0 -device eTSEC,netdev=net0
Root file system on flash drive
-------------------------------
Rather than using a root file system on ram disk, it is possible to have it on
CFI flash. Given an ext2 image whose size must be a power of two, it can be used
as follows:
.. code-block:: bash
$ qemu-system-ppc64 -M ppce500 -cpu e500mc -smp 4 -m 2G \
-display none -serial stdio \
-kernel vmlinux \
-drive if=pflash,file=/path/to/rootfs.ext2,format=raw \
-append "rootwait root=/dev/mtdblock0"
|
