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

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 <[email protected]>

---
 .../devicetree/bindings/arm/fw-cfg.txt        | 38 -------------
 .../bindings/firmware/qemu,fw-cfg-mmio.yaml   | 54 +++++++++++++++++++
 2 files changed, 54 insertions(+), 38 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/arm/fw-cfg.txt
 create mode 100644 Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml

Documentation/devicetree/bindings/arm/fw-cfg.txt deleted +0 -38

deleted file mode 100644
index fd54e1db2156..000000000000
@@ -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 new file +0 -0

new file mode 100644
index 000000000000..3aac9448e7f1

Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml new file +44 -0

+
+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>;
+    };
+...

Quoted 63 lines · Rob Herring

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 <[email protected]>

---
 .../devicetree/bindings/arm/fw-cfg.txt        | 38 -------------
 .../bindings/firmware/qemu,fw-cfg-mmio.yaml   | 54 +++++++++++++++++++
 2 files changed, 54 insertions(+), 38 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/arm/fw-cfg.txt
 create mode 100644 Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml

Documentation/devicetree/bindings/arm/fw-cfg.txt deleted +0 -38

deleted file mode 100644
index fd54e1db2156..000000000000
@@ -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 new file +0 -0

new file mode 100644
index 000000000000..3aac9448e7f1

Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml line 10

Quoted 10 lines

Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml new file +10 -0

@@ -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:
+  - Laszlo Ersek <[email protected]>

Ugh :) I guess this is based on my authorship of historical commit 53275a61bc7a ("devicetree: document ARM bindings for QEMU's Firmware Config interface", 2015-01-13), and prehaps my R-b on commit 92aed5d6ba90 ("devicetree: update documentation for fw_cfg ARM bindings", 2016-02-09).

However -- I totally can't maintain this file. (I mean I've probably not done anything related to it in the past seven years, so I guess it's time to admit that fact!)

Rob, would you please consider taking it over?

With my name+email replaced with yours:

Acked-by Laszlo Ersek <[email protected]>

Thank you!
Laszlo

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 <[email protected]>

---
 .../devicetree/bindings/arm/fw-cfg.txt        | 38 -------------
 .../bindings/firmware/qemu,fw-cfg-mmio.yaml   | 54 +++++++++++++++++++
 2 files changed, 54 insertions(+), 38 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/arm/fw-cfg.txt
 create mode 100644 Documentation/devicetree/bindings/firmware/qemu,fw-cfg-mmio.yaml