1 # SPDX-License-Identifier: GPL-2.0
4 $id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#
5 $schema: http://devicetree.org/meta-schemas/core.yaml#
7 title: QEMU Firmware Configuration bindings
10 - Rob Herring <robh@kernel.org>
13 Various QEMU emulation / virtualization targets provide the following
14 Firmware Configuration interface on the "virt" machine type:
16 - A write-only, 16-bit wide selector (or control) register,
17 - a read-write, 64-bit wide data register.
19 QEMU exposes the control and data register to guests as memory mapped
20 registers; their location is communicated to the guest's UEFI firmware in the
21 DTB that QEMU places at the bottom of the guest's DRAM.
23 The authoritative guest-side hardware interface documentation to the fw_cfg
24 device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree.
29 const: qemu,fw-cfg-mmio
34 * Bytes 0x0 to 0x7 cover the data register.
35 * Bytes 0x8 to 0x9 cover the selector register.
36 * Further registers may be appended to the region in case of future interface
37 revisions / feature bits.
45 additionalProperties: false
51 compatible = "qemu,fw-cfg-mmio";
52 reg = <0x9020000 0xa>;