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.