1CAN Bus Emulation Support 2========================= 3The CAN bus emulation provides mechanism to connect multiple 4emulated CAN controller chips together by one or multiple CAN busses 5(the controller device "canbus" parameter). The individual busses 6can be connected to host system CAN API (at this time only Linux 7SocketCAN is supported). 8 9The concept of busses is generic and different CAN controllers 10can be implemented. 11 12The initial submission implemented SJA1000 controller which 13is common and well supported by by drivers for the most operating 14systems. 15 16The PCI addon card hardware has been selected as the first CAN 17interface to implement because such device can be easily connected 18to systems with different CPU architectures (x86, PowerPC, Arm, etc.). 19 20In 2020, CTU CAN FD controller model has been added as part 21of the bachelor thesis of Jan Charvat. This controller is complete 22open-source/design/hardware solution. The core designer 23of the project is Ondrej Ille, the financial support has been 24provided by CTU, and more companies including Volkswagen subsidiaries. 25 26The project has been initially started in frame of RTEMS GSoC 2013 27slot by Jin Yang under our mentoring The initial idea was to provide generic 28CAN subsystem for RTEMS. But lack of common environment for code and RTEMS 29testing lead to goal change to provide environment which provides complete 30emulated environment for testing and RTEMS GSoC slot has been donated 31to work on CAN hardware emulation on QEMU. 32 33Examples how to use CAN emulation for SJA1000 based boards 34---------------------------------------------------------- 35When QEMU with CAN PCI support is compiled then one of the next 36CAN boards can be selected 37 38(1) CAN bus Kvaser PCI CAN-S (single SJA1000 channel) board. QEMU startup options:: 39 40 -object can-bus,id=canbus0 41 -device kvaser_pci,canbus=canbus0 42 43Add "can-host-socketcan" object to connect device to host system CAN bus:: 44 45 -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 46 47(2) CAN bus PCM-3680I PCI (dual SJA1000 channel) emulation:: 48 49 -object can-bus,id=canbus0 50 -device pcm3680_pci,canbus0=canbus0,canbus1=canbus0 51 52Another example:: 53 54 -object can-bus,id=canbus0 55 -object can-bus,id=canbus1 56 -device pcm3680_pci,canbus0=canbus0,canbus1=canbus1 57 58(3) CAN bus MIOe-3680 PCI (dual SJA1000 channel) emulation:: 59 60 -device mioe3680_pci,canbus0=canbus0 61 62The ''kvaser_pci'' board/device model is compatible with and has been tested with 63the ''kvaser_pci'' driver included in mainline Linux kernel. 64The tested setup was Linux 4.9 kernel on the host and guest side. 65 66Example for qemu-system-x86_64:: 67 68 qemu-system-x86_64 -accel kvm -kernel /boot/vmlinuz-4.9.0-4-amd64 \ 69 -initrd ramdisk.cpio \ 70 -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ 71 -object can-bus,id=canbus0 \ 72 -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \ 73 -device kvaser_pci,canbus=canbus0 \ 74 -nographic -append "console=ttyS0" 75 76Example for qemu-system-arm:: 77 78 qemu-system-arm -cpu arm1176 -m 256 -M versatilepb \ 79 -kernel kernel-qemu-arm1176-versatilepb \ 80 -hda rpi-wheezy-overlay \ 81 -append "console=ttyAMA0 root=/dev/sda2 ro init=/sbin/init-overlay" \ 82 -nographic \ 83 -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ 84 -object can-bus,id=canbus0 \ 85 -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \ 86 -device kvaser_pci,canbus=canbus0,host=can0 \ 87 88The CAN interface of the host system has to be configured for proper 89bitrate and set up. Configuration is not propagated from emulated 90devices through bus to the physical host device. Example configuration 91for 1 Mbit/s:: 92 93 ip link set can0 type can bitrate 1000000 94 ip link set can0 up 95 96Virtual (host local only) can interface can be used on the host 97side instead of physical interface:: 98 99 ip link add dev can0 type vcan 100 101The CAN interface on the host side can be used to analyze CAN 102traffic with "candump" command which is included in "can-utils":: 103 104 candump can0 105 106CTU CAN FD support examples 107--------------------------- 108This open-source core provides CAN FD support. CAN FD drames are 109delivered even to the host systems when SocketCAN interface is found 110CAN FD capable. 111 112The PCIe board emulation is provided for now (the device identifier is 113ctucan_pci). The default build defines two CTU CAN FD cores 114on the board. 115 116Example how to connect the canbus0-bus (virtual wire) to the host 117Linux system (SocketCAN used) and to both CTU CAN FD cores emulated 118on the corresponding PCI card expects that host system CAN bus 119is setup according to the previous SJA1000 section:: 120 121 qemu-system-x86_64 -enable-kvm -kernel /boot/vmlinuz-4.19.52+ \ 122 -initrd ramdisk.cpio \ 123 -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ 124 -vga cirrus \ 125 -append "console=ttyS0" \ 126 -object can-bus,id=canbus0-bus \ 127 -object can-host-socketcan,if=can0,canbus=canbus0-bus,id=canbus0-socketcan \ 128 -device ctucan_pci,canbus0=canbus0-bus,canbus1=canbus0-bus \ 129 -nographic 130 131Setup of CTU CAN FD controller in a guest Linux system:: 132 133 insmod ctucanfd.ko || modprobe ctucanfd 134 insmod ctucanfd_pci.ko || modprobe ctucanfd_pci 135 136 for ifc in /sys/class/net/can* ; do 137 if [ -e $ifc/device/vendor ] ; then 138 if ! grep -q 0x1760 $ifc/device/vendor ; then 139 continue; 140 fi 141 else 142 continue; 143 fi 144 if [ -e $ifc/device/device ] ; then 145 if ! grep -q 0xff00 $ifc/device/device ; then 146 continue; 147 fi 148 else 149 continue; 150 fi 151 ifc=$(basename $ifc) 152 /bin/ip link set $ifc type can bitrate 1000000 dbitrate 10000000 fd on 153 /bin/ip link set $ifc up 154 done 155 156The test can run for example:: 157 158 candump can1 159 160in the guest system and next commands in the host system for basic CAN:: 161 162 cangen can0 163 164for CAN FD without bitrate switch:: 165 166 cangen can0 -f 167 168and with bitrate switch:: 169 170 cangen can0 -b 171 172The test can also be run the other way around, generating messages in the 173guest system and capturing them in the host system. Other combinations are 174also possible. 175 176Links to other resources 177------------------------ 178 179 (1) `CAN related projects at Czech Technical University, Faculty of Electrical Engineering <http://canbus.pages.fel.cvut.cz>`_ 180 (2) `Repository with development can-pci branch at Czech Technical University <https://gitlab.fel.cvut.cz/canbus/qemu-canbus>`_ 181 (3) `RTEMS page describing project <https://devel.rtems.org/wiki/Developer/Simulators/QEMU/CANEmulation>`_ 182 (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>`_ 183 (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>`_ 184 (6) `Linux SocketCAN utilities <https://github.com/linux-can/can-utils>`_ 185 (7) `CTU CAN FD project including core VHDL design, Linux driver, test utilities etc. <https://gitlab.fel.cvut.cz/canbus/ctucanfd_ip_core>`_ 186 (8) `CTU CAN FD Core Datasheet Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/doc/Datasheet.pdf>`_ 187 (9) `CTU CAN FD Core System Architecture Documentation <http://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/doc/System_Architecture.pdf>`_ 188 (10) `CTU CAN FD Driver Documentation <https://canbus.pages.fel.cvut.cz/ctucanfd_ip_core/doc/linux_driver/build/ctucanfd-driver.html>`_ 189 (11) `Integration with PCIe interfacing for Intel/Altera Cyclone IV based board <https://gitlab.fel.cvut.cz/canbus/pcie-ctu_can_fd>`_ 190