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docs/can: convert to restructuredText
Buglink: https://gitlab.com/qemu-project/qemu/-/issues/527 Signed-off-by: Lucas Ramage <lucas.ramage@infinite-omicron.com> Message-id: 20220105205628.5491-1-oxr463@gmx.us Reviewed-by: Peter Maydell <peter.maydell@linaro.org> [PMM: Move to docs/system/devices/ rather than top-level; fix a pre-existing typo in passing] Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
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Peter Maydell
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docs/system/devices/can.rst
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docs/system/devices/can.rst
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CAN Bus Emulation Support
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=========================
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The CAN bus emulation provides mechanism to connect multiple
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emulated CAN controller chips together by one or multiple CAN busses
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(the controller device "canbus" parameter). The individual busses
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can be connected to host system CAN API (at this time only Linux
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SocketCAN is supported).
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The concept of busses is generic and different CAN controllers
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can be implemented.
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The initial submission implemented SJA1000 controller which
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is common and well supported by by drivers for the most operating
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systems.
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The PCI addon card hardware has been selected as the first CAN
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interface to implement because such device can be easily connected
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to systems with different CPU architectures (x86, PowerPC, Arm, etc.).
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In 2020, CTU CAN FD controller model has been added as part
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of the bachelor thesis of Jan Charvat. This controller is complete
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open-source/design/hardware solution. The core designer
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of the project is Ondrej Ille, the financial support has been
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provided by CTU, and more companies including Volkswagen subsidiaries.
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The project has been initially started in frame of RTEMS GSoC 2013
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slot by Jin Yang under our mentoring The initial idea was to provide generic
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CAN subsystem for RTEMS. But lack of common environment for code and RTEMS
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testing lead to goal change to provide environment which provides complete
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emulated environment for testing and RTEMS GSoC slot has been donated
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to work on CAN hardware emulation on QEMU.
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Examples how to use CAN emulation for SJA1000 based boards
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----------------------------------------------------------
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When QEMU with CAN PCI support is compiled then one of the next
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CAN boards can be selected
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(1) CAN bus Kvaser PCI CAN-S (single SJA1000 channel) board. QEMU startup options::
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-object can-bus,id=canbus0
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-device kvaser_pci,canbus=canbus0
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Add "can-host-socketcan" object to connect device to host system CAN bus::
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-object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0
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(2) CAN bus PCM-3680I PCI (dual SJA1000 channel) emulation::
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-object can-bus,id=canbus0
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-device pcm3680_pci,canbus0=canbus0,canbus1=canbus0
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Another example::
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-object can-bus,id=canbus0
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-object can-bus,id=canbus1
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-device pcm3680_pci,canbus0=canbus0,canbus1=canbus1
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(3) CAN bus MIOe-3680 PCI (dual SJA1000 channel) emulation::
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-device mioe3680_pci,canbus0=canbus0
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The ''kvaser_pci'' board/device model is compatible with and has been tested with
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the ''kvaser_pci'' driver included in mainline Linux kernel.
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The tested setup was Linux 4.9 kernel on the host and guest side.
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Example for qemu-system-x86_64::
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qemu-system-x86_64 -accel kvm -kernel /boot/vmlinuz-4.9.0-4-amd64 \
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-initrd ramdisk.cpio \
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-virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \
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-object can-bus,id=canbus0 \
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-object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \
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-device kvaser_pci,canbus=canbus0 \
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-nographic -append "console=ttyS0"
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Example for qemu-system-arm::
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qemu-system-arm -cpu arm1176 -m 256 -M versatilepb \
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-kernel kernel-qemu-arm1176-versatilepb \
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-hda rpi-wheezy-overlay \
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-append "console=ttyAMA0 root=/dev/sda2 ro init=/sbin/init-overlay" \
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-nographic \
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-virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \
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-object can-bus,id=canbus0 \
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-object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \
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-device kvaser_pci,canbus=canbus0,host=can0 \
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The CAN interface of the host system has to be configured for proper
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bitrate and set up. Configuration is not propagated from emulated
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devices through bus to the physical host device. Example configuration
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for 1 Mbit/s::
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ip link set can0 type can bitrate 1000000
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ip link set can0 up
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Virtual (host local only) can interface can be used on the host
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side instead of physical interface::
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ip link add dev can0 type vcan
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The CAN interface on the host side can be used to analyze CAN
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traffic with "candump" command which is included in "can-utils"::
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candump can0
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CTU CAN FD support examples
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---------------------------
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This open-source core provides CAN FD support. CAN FD drames are
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delivered even to the host systems when SocketCAN interface is found
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CAN FD capable.
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The PCIe board emulation is provided for now (the device identifier is
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ctucan_pci). The default build defines two CTU CAN FD cores
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on the board.
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Example how to connect the canbus0-bus (virtual wire) to the host
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Linux system (SocketCAN used) and to both CTU CAN FD cores emulated
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on the corresponding PCI card expects that host system CAN bus
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is setup according to the previous SJA1000 section::
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qemu-system-x86_64 -enable-kvm -kernel /boot/vmlinuz-4.19.52+ \
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-initrd ramdisk.cpio \
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-virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \
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-vga cirrus \
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-append "console=ttyS0" \
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-object can-bus,id=canbus0-bus \
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-object can-host-socketcan,if=can0,canbus=canbus0-bus,id=canbus0-socketcan \
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-device ctucan_pci,canbus0=canbus0-bus,canbus1=canbus0-bus \
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-nographic
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Setup of CTU CAN FD controller in a guest Linux system::
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insmod ctucanfd.ko || modprobe ctucanfd
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insmod ctucanfd_pci.ko || modprobe ctucanfd_pci
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for ifc in /sys/class/net/can* ; do
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if [ -e $ifc/device/vendor ] ; then
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if ! grep -q 0x1760 $ifc/device/vendor ; then
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continue;
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fi
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else
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continue;
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fi
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if [ -e $ifc/device/device ] ; then
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if ! grep -q 0xff00 $ifc/device/device ; then
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continue;
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fi
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else
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continue;
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fi
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ifc=$(basename $ifc)
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/bin/ip link set $ifc type can bitrate 1000000 dbitrate 10000000 fd on
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/bin/ip link set $ifc up
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done
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The test can run for example::
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candump can1
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in the guest system and next commands in the host system for basic CAN::
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cangen can0
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for CAN FD without bitrate switch::
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cangen can0 -f
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and with bitrate switch::
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cangen can0 -b
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The test can be run viceversa, generate messages in the guest system and capture them
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in the host one and much more combinations.
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Links to other resources
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------------------------
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(1) `CAN related projects at Czech Technical University, Faculty of Electrical Engineering <http://canbus.pages.fel.cvut.cz>`_
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(2) `Repository with development can-pci branch at Czech Technical University <https://gitlab.fel.cvut.cz/canbus/qemu-canbus>`_
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(3) `RTEMS page describing project <https://devel.rtems.org/wiki/Developer/Simulators/QEMU/CANEmulation>`_
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(4) `RTLWS 2015 article about the project and its use with CANopen emulation <http://cmp.felk.cvut.cz/~pisa/can/doc/rtlws-17-pisa-qemu-can.pdf>`_
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(5) `GNU/Linux, CAN and CANopen in Real-time Control Applications Slides from LinuxDays 2017 (include updated RTLWS 2015 content) <https://www.linuxdays.cz/2017/video/Pavel_Pisa-CAN_canopen.pdf>`_
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(6) `Linux SocketCAN utilities <https://github.com/linux-can/can-utils>`_
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(7) `CTU CAN FD project including core VHDL design, Linux driver, test utilities etc. <https://gitlab.fel.cvut.cz/canbus/ctucanfd_ip_core>`_
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(8) `CTU CAN FD Core Datasheet Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/Progdokum.pdf>`_
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(9) `CTU CAN FD Core System Architecture Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/ctu_can_fd_architecture.pdf>`_
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(10) `CTU CAN FD Driver Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/driver_doc/ctucanfd-driver.html>`_
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(11) `Integration with PCIe interfacing for Intel/Altera Cyclone IV based board <https://gitlab.fel.cvut.cz/canbus/pcie-ctu_can_fd>`_
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