108 lines
4.2 KiB
Plaintext
108 lines
4.2 KiB
Plaintext
QEMU 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 for it but at this time only SJA1000 chip
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controller is implemented.
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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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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
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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) boad. 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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''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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Links to other resources
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========================
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(1) Repository with development branch can-pci at Czech Technical University
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https://gitlab.fel.cvut.cz/canbus/qemu-canbus
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(2) GitHub repository with can-pci and our other changes included
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https://gitlab.fel.cvut.cz/canbus/qemu-canbus
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(3) RTEMS page describing project
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https://devel.rtems.org/wiki/Developer/Simulators/QEMU/CANEmulation
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(4) RTLWS 2015 article about the projevt and its use with CANopen emulation
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http://rtime.felk.cvut.cz/publications/public/rtlws2015-qemu-can.pdf
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Slides
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http://rtime.felk.cvut.cz/publications/public/rtlws2015-qemu-can-slides.pdf
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(5) Linux SocketCAN utilities
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https://github.com/linux-can/can-utils/
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