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diff --git a/docs/system/devices/can.rst b/docs/system/devices/can.rst new file mode 100644 index 0000000000..16d72c3ac3 --- /dev/null +++ b/docs/system/devices/can.rst @@ -0,0 +1,188 @@ +CAN Bus Emulation Support +========================= +The CAN bus emulation provides mechanism to connect multiple +emulated CAN controller chips together by one or multiple CAN busses +(the controller device "canbus" parameter). The individual busses +can be connected to host system CAN API (at this time only Linux +SocketCAN is supported). + +The concept of busses is generic and different CAN controllers +can be implemented. + +The initial submission implemented SJA1000 controller which +is common and well supported by by drivers for the most operating +systems. + +The PCI addon card hardware has been selected as the first CAN +interface to implement because such device can be easily connected +to systems with different CPU architectures (x86, PowerPC, Arm, etc.). + +In 2020, CTU CAN FD controller model has been added as part +of the bachelor thesis of Jan Charvat. This controller is complete +open-source/design/hardware solution. The core designer +of the project is Ondrej Ille, the financial support has been +provided by CTU, and more companies including Volkswagen subsidiaries. + +The project has been initially started in frame of RTEMS GSoC 2013 +slot by Jin Yang under our mentoring The initial idea was to provide generic +CAN subsystem for RTEMS. But lack of common environment for code and RTEMS +testing lead to goal change to provide environment which provides complete +emulated environment for testing and RTEMS GSoC slot has been donated +to work on CAN hardware emulation on QEMU. + +Examples how to use CAN emulation for SJA1000 based boards +---------------------------------------------------------- +When QEMU with CAN PCI support is compiled then one of the next +CAN boards can be selected + +(1) CAN bus Kvaser PCI CAN-S (single SJA1000 channel) board. QEMU startup options:: + + -object can-bus,id=canbus0 + -device kvaser_pci,canbus=canbus0 + +Add "can-host-socketcan" object to connect device to host system CAN bus:: + + -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 + +(2) CAN bus PCM-3680I PCI (dual SJA1000 channel) emulation:: + + -object can-bus,id=canbus0 + -device pcm3680_pci,canbus0=canbus0,canbus1=canbus0 + +Another example:: + + -object can-bus,id=canbus0 + -object can-bus,id=canbus1 + -device pcm3680_pci,canbus0=canbus0,canbus1=canbus1 + +(3) CAN bus MIOe-3680 PCI (dual SJA1000 channel) emulation:: + + -device mioe3680_pci,canbus0=canbus0 + +The ''kvaser_pci'' board/device model is compatible with and has been tested with +the ''kvaser_pci'' driver included in mainline Linux kernel. +The tested setup was Linux 4.9 kernel on the host and guest side. + +Example for qemu-system-x86_64:: + + qemu-system-x86_64 -accel kvm -kernel /boot/vmlinuz-4.9.0-4-amd64 \ + -initrd ramdisk.cpio \ + -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ + -object can-bus,id=canbus0 \ + -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \ + -device kvaser_pci,canbus=canbus0 \ + -nographic -append "console=ttyS0" + +Example for qemu-system-arm:: + + qemu-system-arm -cpu arm1176 -m 256 -M versatilepb \ + -kernel kernel-qemu-arm1176-versatilepb \ + -hda rpi-wheezy-overlay \ + -append "console=ttyAMA0 root=/dev/sda2 ro init=/sbin/init-overlay" \ + -nographic \ + -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ + -object can-bus,id=canbus0 \ + -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \ + -device kvaser_pci,canbus=canbus0,host=can0 \ + +The CAN interface of the host system has to be configured for proper +bitrate and set up. Configuration is not propagated from emulated +devices through bus to the physical host device. Example configuration +for 1 Mbit/s:: + + ip link set can0 type can bitrate 1000000 + ip link set can0 up + +Virtual (host local only) can interface can be used on the host +side instead of physical interface:: + + ip link add dev can0 type vcan + +The CAN interface on the host side can be used to analyze CAN +traffic with "candump" command which is included in "can-utils":: + + candump can0 + +CTU CAN FD support examples +--------------------------- +This open-source core provides CAN FD support. CAN FD drames are +delivered even to the host systems when SocketCAN interface is found +CAN FD capable. + +The PCIe board emulation is provided for now (the device identifier is +ctucan_pci). The default build defines two CTU CAN FD cores +on the board. + +Example how to connect the canbus0-bus (virtual wire) to the host +Linux system (SocketCAN used) and to both CTU CAN FD cores emulated +on the corresponding PCI card expects that host system CAN bus +is setup according to the previous SJA1000 section:: + + qemu-system-x86_64 -enable-kvm -kernel /boot/vmlinuz-4.19.52+ \ + -initrd ramdisk.cpio \ + -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ + -vga cirrus \ + -append "console=ttyS0" \ + -object can-bus,id=canbus0-bus \ + -object can-host-socketcan,if=can0,canbus=canbus0-bus,id=canbus0-socketcan \ + -device ctucan_pci,canbus0=canbus0-bus,canbus1=canbus0-bus \ + -nographic + +Setup of CTU CAN FD controller in a guest Linux system:: + + insmod ctucanfd.ko || modprobe ctucanfd + insmod ctucanfd_pci.ko || modprobe ctucanfd_pci + + for ifc in /sys/class/net/can* ; do + if [ -e $ifc/device/vendor ] ; then + if ! grep -q 0x1760 $ifc/device/vendor ; then + continue; + fi + else + continue; + fi + if [ -e $ifc/device/device ] ; then + if ! grep -q 0xff00 $ifc/device/device ; then + continue; + fi + else + continue; + fi + ifc=$(basename $ifc) + /bin/ip link set $ifc type can bitrate 1000000 dbitrate 10000000 fd on + /bin/ip link set $ifc up + done + +The test can run for example:: + + candump can1 + +in the guest system and next commands in the host system for basic CAN:: + + cangen can0 + +for CAN FD without bitrate switch:: + + cangen can0 -f + +and with bitrate switch:: + + cangen can0 -b + +The test can be run viceversa, generate messages in the guest system and capture them +in the host one and much more combinations. + +Links to other resources +------------------------ + + (1) `CAN related projects at Czech Technical University, Faculty of Electrical Engineering <http://canbus.pages.fel.cvut.cz>`_ + (2) `Repository with development can-pci branch at Czech Technical University <https://gitlab.fel.cvut.cz/canbus/qemu-canbus>`_ + (3) `RTEMS page describing project <https://devel.rtems.org/wiki/Developer/Simulators/QEMU/CANEmulation>`_ + (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>`_ + (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>`_ + (6) `Linux SocketCAN utilities <https://github.com/linux-can/can-utils>`_ + (7) `CTU CAN FD project including core VHDL design, Linux driver, test utilities etc. <https://gitlab.fel.cvut.cz/canbus/ctucanfd_ip_core>`_ + (8) `CTU CAN FD Core Datasheet Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/Progdokum.pdf>`_ + (9) `CTU CAN FD Core System Architecture Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/ctu_can_fd_architecture.pdf>`_ + (10) `CTU CAN FD Driver Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/driver_doc/ctucanfd-driver.html>`_ + (11) `Integration with PCIe interfacing for Intel/Altera Cyclone IV based board <https://gitlab.fel.cvut.cz/canbus/pcie-ctu_can_fd>`_ |