1Arm Server Base System Architecture Reference board (``sbsa-ref``) 2================================================================== 3 4While the ``virt`` board is a generic board platform that doesn't match 5any real hardware the ``sbsa-ref`` board intends to look like real 6hardware. The `Server Base System Architecture 7<https://developer.arm.com/documentation/den0029/latest>`_ defines a 8minimum base line of hardware support and importantly how the firmware 9reports that to any operating system. 10 11It is intended to be a machine for developing firmware and testing 12standards compliance with operating systems. 13 14Supported devices 15""""""""""""""""" 16 17The ``sbsa-ref`` board supports: 18 19 - A configurable number of AArch64 CPUs 20 - GIC version 3 21 - System bus AHCI controller 22 - System bus EHCI controller 23 - CDROM and hard disc on AHCI bus 24 - E1000E ethernet card on PCIe bus 25 - Bochs display adapter on PCIe bus 26 - A generic SBSA watchdog device 27 28 29Board to firmware interface 30""""""""""""""""""""""""""" 31 32``sbsa-ref`` is a static system that reports a very minimal devicetree to the 33firmware for non-discoverable information about system components. This 34includes both internal hardware and parts affected by the qemu command line 35(i.e. CPUs and memory). As a result it must have a firmware specifically built 36to expect a certain hardware layout (as you would in a real machine). 37 38DeviceTree information 39'''''''''''''''''''''' 40 41The devicetree provided by the board model to the firmware is not intended 42to be a complete compliant DT. It currently reports: 43 44 - CPUs 45 - memory 46 - platform version 47 - GIC addresses 48 49Platform version 50'''''''''''''''' 51 52The platform version is only for informing platform firmware about 53what kind of ``sbsa-ref`` board it is running on. It is neither 54a QEMU versioned machine type nor a reflection of the level of the 55SBSA/SystemReady SR support provided. 56 57The ``machine-version-major`` value is updated when changes breaking 58fw compatibility are introduced. The ``machine-version-minor`` value 59is updated when features are added that don't break fw compatibility. 60 61Platform version changes: 62 630.0 64 Devicetree holds information about CPUs, memory and platform version. 65 660.1 67 GIC information is present in devicetree. 68 690.2 70 GIC ITS information is present in devicetree. 71