[PATCH 5/5] xen/arm: add dom0less device assignment info to docs

[Stefano Stabellini <sstabellini@kernel.org>]

Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
---
 docs/misc/arm/device-tree/booting.txt | 108 ++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt
index 317a9e9..f5aaf8f 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -226,3 +226,111 @@ chosen {
         };
     };
 };
+
+
+Device Assignment
+=================
+
+Device Assignment (Passthrough) is supported by adding another module,
+alongside the kernel and ramdisk, with the device tree fragment
+corresponding to the device node to assign to the guest.
+
+The dtb sub-node should have the following properties:
+
+- compatible
+
+    "multiboot,dtb"
+
+- reg
+
+    Specifies the physical address of the device tree binary fragment
+    RAM and its length.
+
+As an example:
+
+        module@0xc000000 {
+            compatible = "multiboot,dtb", "multiboot,module";
+            reg = <0x0 0xc000000 0xffffff>;
+        };
+
+The DTB fragment (loaded in memory at 0xc000000 in the example above)
+should follow the convention explained in docs/misc/arm/passthrough.txt.
+The DTB fragment will be added to the guest device tree, so that the
+guest kernel will be able to discover the device.
+
+In addition, the following properties for each device node in the device
+tree fragment will be used for the device assignment setup:
+
+- reg
+
+  The reg property specifying the address and size of the device memory.
+  The device memory will be automatically mapped to the guest domain
+  with a 1:1 mapping (pseudo-physical address == physical address).
+
+- interrupts
+
+  The interrupts property specifies the interrupt of the device. They
+  are automatically routed to the guest domain with virtual irqs ==
+  physical irqs.
+
+- interrupt-parent
+
+  It contains a reference to the interrupt controller node. It should be
+  65000, corresponding to GUEST_PHANDLE_GIC.
+
+- path
+
+  A new string property named "path" holds the path in the host device
+  tree to the corresponding device node.
+
+The following is a real-world example of a device tree fragment for the
+network card on Xilinx MPSoC boards:
+
+/dts-v1/;
+
+/ {
+    #address-cells = <0x2>;
+    #size-cells = <0x1>;
+
+    passthrough {
+        compatible = "simple-bus";
+        ranges;
+        #address-cells = <0x2>;
+        #size-cells = <0x1>;
+
+        misc_clk {
+            #clock-cells = <0x0>;
+            clock-frequency = <0x7735940>;
+            compatible = "fixed-clock";
+            linux,phandle = <0x1>;
+            phandle = <0x1>;
+        };
+
+        ethernet@ff0e0000 {
+            compatible = "cdns,zynqmp-gem";
+            status = "okay";
+            interrupt-parent = <0xfde8>;
+            interrupts = <0x0 0x3f 0x4 0x0 0x3f 0x4>;
+            reg = <0x0 0xff0e0000 0x1000>;
+            clock-names = "pclk", "hclk", "tx_clk", "rx_clk";
+            #address-cells = <0x1>;
+            #size-cells = <0x0>;
+            clocks = <0x1 0x1 0x1 0x1>;
+            phy-mode = "rgmii-id";
+            xlnx,ptp-enet-clock = <0x0>;
+            local-mac-address = [00 0a 35 00 22 01];
+            phy-handle = <0x2>;
+            path = "/amba/ethernet@ff0e0000";
+
+            phy@c {
+                reg = <0xc>;
+                ti,rx-internal-delay = <0x8>;
+                ti,tx-internal-delay = <0xa>;
+                ti,fifo-depth = <0x1>;
+                ti,rxctrl-strap-worka;
+                linux,phandle = <0x2>;
+                phandle = <0x2>;
+            };
+        };
+    };
+};
-- 
1.9.1


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