1 # SPDX-License-Identifier: GPL-2.0 1 # SPDX-License-Identifier: GPL-2.0
2 %YAML 1.2 2 %YAML 1.2
3 --- 3 ---
4 $id: http://devicetree.org/schemas/firmware/qe 4 $id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#
5 $schema: http://devicetree.org/meta-schemas/co 5 $schema: http://devicetree.org/meta-schemas/core.yaml#
6 6
7 title: QEMU Firmware Configuration 7 title: QEMU Firmware Configuration
8 8
9 maintainers: 9 maintainers:
10 - Rob Herring <robh@kernel.org> 10 - Rob Herring <robh@kernel.org>
11 11
12 description: | 12 description: |
13 Various QEMU emulation / virtualization targ 13 Various QEMU emulation / virtualization targets provide the following
14 Firmware Configuration interface on the "vir 14 Firmware Configuration interface on the "virt" machine type:
15 15
16 - A write-only, 16-bit wide selector (or con 16 - A write-only, 16-bit wide selector (or control) register,
17 - a read-write, 64-bit wide data register. 17 - a read-write, 64-bit wide data register.
18 18
19 QEMU exposes the control and data register t 19 QEMU exposes the control and data register to guests as memory mapped
20 registers; their location is communicated to 20 registers; their location is communicated to the guest's UEFI firmware in the
21 DTB that QEMU places at the bottom of the gu 21 DTB that QEMU places at the bottom of the guest's DRAM.
22 22
23 The authoritative guest-side hardware interf 23 The authoritative guest-side hardware interface documentation to the fw_cfg
24 device can be found in "docs/specs/fw_cfg.tx 24 device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree.
25 25
26 26
27 properties: 27 properties:
28 compatible: 28 compatible:
29 const: qemu,fw-cfg-mmio 29 const: qemu,fw-cfg-mmio
30 30
31 reg: 31 reg:
32 maxItems: 1 32 maxItems: 1
33 description: | 33 description: |
34 * Bytes 0x0 to 0x7 cover the data regist 34 * Bytes 0x0 to 0x7 cover the data register.
35 * Bytes 0x8 to 0x9 cover the selector re 35 * Bytes 0x8 to 0x9 cover the selector register.
36 * Further registers may be appended to t 36 * Further registers may be appended to the region in case of future interface
37 revisions / feature bits. 37 revisions / feature bits.
38 38
39 dma-coherent: true 39 dma-coherent: true
40 40
41 required: 41 required:
42 - compatible 42 - compatible
43 - reg 43 - reg
44 44
45 additionalProperties: false 45 additionalProperties: false
46 46
47 examples: 47 examples:
48 - | 48 - |
49 49
50 fw-cfg@9020000 { 50 fw-cfg@9020000 {
51 compatible = "qemu,fw-cfg-mmio"; 51 compatible = "qemu,fw-cfg-mmio";
52 reg = <0x9020000 0xa>; 52 reg = <0x9020000 0xa>;
53 }; 53 };
54 ... 54 ...
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