path: root/dts/Bindings/arm
diff options
authorSascha Hauer <>2015-02-09 08:46:06 +0100
committerSascha Hauer <>2015-02-11 09:50:08 +0100
commita3a33ebc1c464c6ce7530dc440529e56ac5d5eb4 (patch)
tree97be27f531d58ff9730e89f5ad160002a7176199 /dts/Bindings/arm
parent52329fa2e32ac80dcf8ff0906d32cc6b77c30f1e (diff)
dts: update to v3.19-rc6
Signed-off-by: Sascha Hauer <>
Diffstat (limited to 'dts/Bindings/arm')
2 files changed, 73 insertions, 1 deletions
diff --git a/dts/Bindings/arm/arm-boards b/dts/Bindings/arm/arm-boards
index 556c866..b78564b 100644
--- a/dts/Bindings/arm/arm-boards
+++ b/dts/Bindings/arm/arm-boards
@@ -23,7 +23,7 @@ Required nodes:
range of 0x200 bytes.
- syscon: the root node of the Integrator platforms must have a
- system controller node pointong to the control registers,
+ system controller node pointing to the control registers,
with the compatible string
diff --git a/dts/Bindings/arm/fw-cfg.txt b/dts/Bindings/arm/fw-cfg.txt
new file mode 100644
index 0000000..953fb64
--- /dev/null
+++ b/dts/Bindings/arm/fw-cfg.txt
@@ -0,0 +1,72 @@
+* 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
+- 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 guest writes a selector value (a key) to the selector register, and then
+can read the corresponding data (produced by QEMU) via the data register. If
+the selected entry is writable, the guest can rewrite it through the data
+The selector register takes keys in big endian byte order.
+The data register allows accesses with 8, 16, 32 and 64-bit width (only at
+offset 0 of the register). Accesses larger than a byte are interpreted as
+arrays, bundled together only for better performance. The bytes constituting
+such a word, in increasing address order, correspond to the bytes that would
+have been transferred by byte-wide accesses in chronological order.
+The interface allows guest firmware to download various parameters and blobs
+that affect how the firmware works and what tables it installs for the guest
+OS. For example, boot order of devices, ACPI tables, SMBIOS tables, kernel and
+initrd images for direct kernel booting, virtual machine UUID, SMP information,
+virtual NUMA topology, and so on.
+The authoritative registry of the valid selector values and their meanings is
+the QEMU source code; the structure of the data blobs corresponding to the
+individual key values is also defined in the QEMU source code.
+The presence of the registers can be verified by selecting the "signature" blob
+with key 0x0000, and reading four bytes from the data register. The returned
+signature is "QEMU".
+The outermost protocol (involving the write / read sequences of the control and
+data registers) is expected to be versioned, and/or described by feature bits.
+The interface revision / feature bitmap can be retrieved with key 0x0001. The
+blob to be read from the data register has size 4, and it is to be interpreted
+as a uint32_t value in little endian byte order. The current value
+(corresponding to the above outer protocol) is zero.
+The guest kernel is not expected to use these registers (although it is
+certainly allowed to); the device tree bindings are documented here because
+this is where device tree bindings reside in general.
+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.
+/ {
+ #size-cells = <0x2>;
+ #address-cells = <0x2>;
+ fw-cfg@9020000 {
+ compatible = "qemu,fw-cfg-mmio";
+ reg = <0x0 0x9020000 0x0 0xa>;
+ };