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dt-bindings: arm: Convert QEMU fw-cfg to DT schema

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Convert the QEMU fw-cfg binding to DT schema format. As this binding is
also used on Risc-V now, drop any architecture references and move to a
common location. The fw-cfg interface has also gained some DMA support
which is coherent, so add the missing 'dma-coherent'.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Link: https://lore.kernel.org/r/20220310013552.549590-1-robh@kernel.org
This commit is contained in:
Rob Herring
2022-03-09 19:35:52 -06:00
parent 2a4013c0cc
commit 1d9a770bc8
2 changed files with 54 additions and 38 deletions
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Documentation/devicetree/bindings/arm/fw-cfg.txt
-38
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@@ -1,38 +0,0 @@
* QEMU Firmware Configuration bindings for ARM
QEMU's arm-softmmu and aarch64-softmmu emulation / virtualization targets
provide the following Firmware Configuration interface on the "virt" machine
type:
- A write-only, 16-bit wide selector (or control) register,
- a read-write, 64-bit wide data register.
QEMU exposes the control and data register to ARM guests as memory mapped
registers; their location is communicated to the guest's UEFI firmware in the
DTB that QEMU places at the bottom of the guest's DRAM.
The authoritative guest-side hardware interface documentation to the fw_cfg
device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree.
Required properties:
- compatible: "qemu,fw-cfg-mmio".
- reg: the MMIO region used by the device.
* Bytes 0x0 to 0x7 cover the data register.
* Bytes 0x8 to 0x9 cover the selector register.
* Further registers may be appended to the region in case of future interface
revisions / feature bits.
Example:
/ {
#size-cells = <0x2>;
#address-cells = <0x2>;
fw-cfg@9020000 {
compatible = "qemu,fw-cfg-mmio";
reg = <0x0 0x9020000 0x0 0xa>;
};
};
Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml
+54
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@@ -0,0 +1,54 @@
# SPDX-License-Identifier: GPL-2.0
%YAML 1.2
---
$id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title: QEMU Firmware Configuration bindings
maintainers:
- Rob Herring <robh@kernel.org>
description: |
Various QEMU emulation / virtualization targets provide the following
Firmware Configuration interface on the "virt" machine type:
- A write-only, 16-bit wide selector (or control) register,
- a read-write, 64-bit wide data register.
QEMU exposes the control and data register to guests as memory mapped
registers; their location is communicated to the guest's UEFI firmware in the
DTB that QEMU places at the bottom of the guest's DRAM.
The authoritative guest-side hardware interface documentation to the fw_cfg
device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree.
properties:
compatible:
const: qemu,fw-cfg-mmio
reg:
maxItems: 1
description: |
* Bytes 0x0 to 0x7 cover the data register.
* Bytes 0x8 to 0x9 cover the selector register.
* Further registers may be appended to the region in case of future interface
revisions / feature bits.
dma-coherent: true
required:
- compatible
- reg
additionalProperties: false
examples:
- |
fw-cfg@9020000 {
compatible = "qemu,fw-cfg-mmio";
reg = <0x9020000 0xa>;
};
...