Tux on Zynq

U-BOOT

Templates

The zturn board specific files are largely based upon

zynq_zed_defconfig found in https://codeload.github.com/Xilinx/u-boot-xlnx/tar.gz/xilinx-v2019.2
https://github.com/Xilinx/u-boot-xlnx/blob/master/arch/arm/dts/zynq-zed.dts

To change u-boot configuration, run make uboot-repo and then change to build/name.uboot/ and run

make menuconfig

The changes made are stored in .config. To export only the values change, run

make savedefconfig

and store the generated defconfig file in the corresponding boards/name/uboot folder.

Literature

On minimal linux systems with kernel & initramfs:

Zynq Linux device drivers:

https://www.youtube.com/watch?v=h-ZP98qhEM8

Knowledge

Device Tree

A good starting point is here with more here.

Example: Ethernet

The ethernet controller did not work on u-boot out of the box. The ethernet phy had to be added to the device tree. Identified as micrel ksz9031 part on the board, the dts can be modified.

The root dts zynq-7000.dtsi included by zturn_7010.dts defines the Zynq's integrated ethernet controller as followed:

/ {
	cpus {
		// ....
	};
	// ....
	amba: amba {
		u-boot,dm-pre-reloc;
		compatible = "simple-bus";
		#address-cells = <1>;
		#size-cells = <1>;
		interrupt-parent = <&intc>;
		ranges;
		// ....
		gem0: ethernet@e000b000 {
			compatible = "cdns,zynq-gem", "cdns,gem";
			reg = <0xe000b000 0x1000>;
			status = "disabled";
			interrupts = <0 22 4>;
			clocks = <&clkc 30>, <&clkc 30>, <&clkc 13>;
			clock-names = "pclk", "hclk", "tx_clk";
			#address-cells = <1>;
			#size-cells = <0>;
		};
		// ....
	};
};

Xilinx's Zynq TRM UG585 specifies the ethernet controller at e000_b000 which coincides with the definition of gem0. gem0 is a label for ethernet@e000b000 that we can later use to add devices to the ethernet controller.

From this declaration we find that #address-cells = <1> meaning that any child-node must define a reg with one address cell and zero size cells #size-cells = <0>. The PHY address is specified in the datasheet. In my case, the address can be configured with package pins, but the schematic doesn't show this connection. After running u-boot without the reg declaration, the mii info command listed the PHY:

PHY 0x03: OUI = 0x0885, Model = 0x22, Rev = 0x02, 100baseT, FDX

A read at the device identifier address, shows the correct phy:

zturn> mii read 3 0x2-0x3
addr=03 reg=02 data=0022
addr=03 reg=03 data=1622

We can now append information to the gem0 node to get the PHY running:

&gem0 {
	status = "okay";
	phy-mode = "rgmii-id";
	phy-handle = <&ethernet_phy>;

	ethernet_phy: ethernet-phy@0 {
		reg = <3>;
		compatible = "micrel,ksz9031";
		device_type = "ethernet-phy";
	};
};

JTAG debugging in console

The ps7_init.tcl can be extracted from the xsa zip file. Some commands can be found here.

Set boot mode to JTAG

huettern/tux-on-zynq