   d) Xilinx IP cores

   The Xilinx EDK toolchain ships with a set of IP cores (devices) for use
   in Xilinx Spartan and Virtex FPGAs.  The devices cover the whole range
   of standard device types (network, serial, etc.) and miscellaneous
   devices (gpio, LCD, spi, etc).  Also, since these devices are
   implemented within the fpga fabric every instance of the device can be
   synthesised with different options that change the behaviour.

   Each IP-core has a set of parameters which the FPGA designer can use to
   control how the core is synthesized.  Historically, the EDK tool would
   extract the device parameters relevant to device drivers and copy them
   into an 'xparameters.h' in the form of #define symbols.  This tells the
   device drivers how the IP cores are configured, but it requires the kernel
   to be recompiled every time the FPGA bitstream is resynthesized.

   The new approach is to export the parameters into the device tree and
   generate a new device tree each time the FPGA bitstream changes.  The
   parameters which used to be exported as #defines will now become
   properties of the device node.  In general, device nodes for IP-cores
   will take the following form:

	(name): (generic-name)@(base-address) {
		compatible = "xlnx,(ip-core-name)-(HW_VER)"
			     [, (list of compatible devices), ...];
		reg = <(baseaddr) (size)>;
		interrupt-parent = <&interrupt-controller-phandle>;
		interrupts = < ... >;
		xlnx,(parameter1) = "(string-value)";
		xlnx,(parameter2) = <(int-value)>;
	};

	(generic-name):   an open firmware-style name that describes the
			generic class of device.  Preferably, this is one word, such
			as 'serial' or 'ethernet'.
	(ip-core-name):	the name of the ip block (given after the BEGIN
			directive in system.mhs).  Should be in lowercase
			and all underscores '_' converted to dashes '-'.
	(name):		is derived from the "PARAMETER INSTANCE" value.
	(parameter#):	C_* parameters from system.mhs.  The C_ prefix is
			dropped from the parameter name, the name is converted
			to lowercase and all underscore '_' characters are
			converted to dashes '-'.
	(baseaddr):	the baseaddr parameter value (often named C_BASEADDR).
	(HW_VER):	from the HW_VER parameter.
	(size):		the address range size (often C_HIGHADDR - C_BASEADDR + 1).

   Typically, the compatible list will include the exact IP core version
   followed by an older IP core version which implements the same
   interface or any other device with the same interface.

   'reg' and 'interrupts' are all optional properties.

   For example, the following block from system.mhs:

	BEGIN opb_uartlite
		PARAMETER INSTANCE = opb_uartlite_0
		PARAMETER HW_VER = 1.00.b
		PARAMETER C_BAUDRATE = 115200
		PARAMETER C_DATA_BITS = 8
		PARAMETER C_ODD_PARITY = 0
		PARAMETER C_USE_PARITY = 0
		PARAMETER C_CLK_FREQ = 50000000
		PARAMETER C_BASEADDR = 0xEC100000
		PARAMETER C_HIGHADDR = 0xEC10FFFF
		BUS_INTERFACE SOPB = opb_7
		PORT OPB_Clk = CLK_50MHz
		PORT Interrupt = opb_uartlite_0_Interrupt
		PORT RX = opb_uartlite_0_RX
		PORT TX = opb_uartlite_0_TX
		PORT OPB_Rst = sys_bus_reset_0
	END

   becomes the following device tree node:

	opb_uartlite_0: serial@ec100000 {
		device_type = "serial";
		compatible = "xlnx,opb-uartlite-1.00.b";
		reg = <ec100000 10000>;
		interrupt-parent = <&opb_intc_0>;
		interrupts = <1 0>; // got this from the opb_intc parameters
		current-speed = <d#115200>;	// standard serial device prop
		clock-frequency = <d#50000000>;	// standard serial device prop
		xlnx,data-bits = <8>;
		xlnx,odd-parity = <0>;
		xlnx,use-parity = <0>;
	};

   That covers the general approach to binding xilinx IP cores into the
   device tree.  The following are bindings for specific devices:

      i) Xilinx ML300 Framebuffer

      Simple framebuffer device from the ML300 reference design (also on the
      ML403 reference design as well as others).

      Optional properties:
       - resolution = <xres yres> : pixel resolution of framebuffer.  Some
                                    implementations use a different resolution.
                                    Default is <d#640 d#480>
       - virt-resolution = <xvirt yvirt> : Size of framebuffer in memory.
                                           Default is <d#1024 d#480>.
       - rotate-display (empty) : rotate display 180 degrees.

      ii) Xilinx SystemACE

      The Xilinx SystemACE device is used to program FPGAs from an FPGA
      bitstream stored on a CF card.  It can also be used as a generic CF
      interface device.

      Optional properties:
       - 8-bit (empty) : Set this property for SystemACE in 8 bit mode

      iii) Xilinx EMAC and Xilinx TEMAC

      Xilinx Ethernet devices.  In addition to general xilinx properties
      listed above, nodes for these devices should include a phy-handle
      property, and may include other common network device properties
      like local-mac-address.

      iv) Xilinx Uartlite

      Xilinx uartlite devices are simple fixed speed serial ports.

      Required properties:
       - current-speed : Baud rate of uartlite

      v) Xilinx hwicap

		Xilinx hwicap devices provide access to the configuration logic
		of the FPGA through the Internal Configuration Access Port
		(ICAP).  The ICAP enables partial reconfiguration of the FPGA,
		readback of the configuration information, and some control over
		'warm boots' of the FPGA fabric.

		Required properties:
		- xlnx,family : The family of the FPGA, necessary since the
                      capabilities of the underlying ICAP hardware
                      differ between different families.  May be
                      'virtex2p', 'virtex4', or 'virtex5'.
		- compatible : should contain "xlnx,xps-hwicap-1.00.a" or
				"xlnx,opb-hwicap-1.00.b".

      vi) Xilinx Uart 16550

      Xilinx UART 16550 devices are very similar to the NS16550 but with
      different register spacing and an offset from the base address.

      Required properties:
       - clock-frequency : Frequency of the clock input
       - reg-offset : A value of 3 is required
       - reg-shift : A value of 2 is required

      vii) Xilinx USB Host controller

      The Xilinx USB host controller is EHCI compatible but with a different
      base address for the EHCI registers, and it is always a big-endian
      USB Host controller. The hardware can be configured as high speed only,
      or high speed/full speed hybrid.

      Required properties:
      - xlnx,support-usb-fs: A value 0 means the core is built as high speed
                             only. A value 1 means the core also supports
                             full speed devices.