qemu,fw-cfg-mmio.yaml

 1# SPDX-License-Identifier: GPL-2.0
 2%YAML 1.2
 3---
 4$id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#
 5$schema: http://devicetree.org/meta-schemas/core.yaml#
 6
 7title: QEMU Firmware Configuration
 8
 9maintainers:
10  - Rob Herring <robh@kernel.org>
11
12description: |
13  Various QEMU emulation / virtualization targets provide the following
14  Firmware Configuration interface on the "virt" machine type:
15
16  - A write-only, 16-bit wide selector (or control) register,
17  - a read-write, 64-bit wide data register.
18
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.
22
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.
25
26properties:
27  compatible:
28    const: qemu,fw-cfg-mmio
29
30  reg:
31    maxItems: 1
32    description: |
33      * Bytes 0x0 to 0x7 cover the data register.
34      * Bytes 0x8 to 0x9 cover the selector register.
35      * Further registers may be appended to the region in case of future interface
36        revisions / feature bits.
37
38  dma-coherent: true
39
40required:
41  - compatible
42  - reg
43
44additionalProperties: false
45
46examples:
47  - |
48
49    fw-cfg@9020000 {
50        compatible = "qemu,fw-cfg-mmio";
51        reg = <0x9020000 0xa>;
52    };
53...