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.. _device-tree/vas:
Virtual Accelerator Switchboard (VAS)
=====================================
VAS is present in P9 or later processors. In P9, each chip has one
instance of VAS. Each instance of VAS is represented as a "platform
device" i.e as a node in root of the device tree: ::
/vas@<vas_addr>
with unique VAS address which also represents the Hypervisor window
context address for the instance of VAS.
Each VAS node contains: ::
compatible: "ibm,power9-vas", "ibm,vas"
ibm,chip-id: Chip-id of the chip containing this instance of VAS.
ibm,vas-id: unique identifier for each instance of VAS in the system.
ibm,vas-port: Port address for the interrupt.
interrupts: <IRQ# level> for this VAS instance.
interrupt-parent: Interrupt controller phandle.
reg: contains 8 64-bit fields.
Fields [0] and [1] represent the Hypervisor window context BAR
(start and length). Fields [2] and [3] represent the OS/User
window context BAR (start and length). Fields [4] and [5]
contain the start and length of paste power bus address region
for this chip. Fields [6] and [7] represent the bit field (start
bit and number of bits) where the window id of the window should
be encoded when computing the paste address for the window.
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