Introduction

Xillinux 1.3 is a good starting point for ZYBO because out-of-the-box it provides:

• Verilog/VHDL design for PL which enables video and audio outputs

• First stage bootloader which uploads bitstream to PL

• Ubuntu 12.04 armhf based root filesystem

• Device tree definition

So why should you want to recompile the kernel? There are various reasons, for instance I happened to buy a USB WiFi dongle that did not work out of the box. If you're attempt to compile a kernel module then you're also in need of a prepared kernel source tree.

About kernel development generally

The kernel development flow for Xillinux 1.3 and ZYBO should approximately adhere to following:

• Linux kernel upstream 1

• Xilinx downstream for Zynq-7000 boards 2

• Digilent downstream for this particular board 3

• Xillybus downstream patches against 3.12 which are sitting under /usr/src/xillinux/kernel-patches/

You may fetch the source using Git:

git clone https://github.com/digilent/linux-Digilent-Dev

If you want to retain working video/audio drivers I suggest you checkout particular kernel version against which Xillinux 1.3 kernel was compiled:

git checkout 7ad8e6023d969336961312ef751228cbb8874752

Then fetch the patches from /usr/src/xillinux/kernel-patches/ and apply them one-by-one:

patch -p1 < 0001-.config-file-added-to-tree.patch
patch -p1 < 0002-Makefile-Added-xillinux-1.3-extra-version-to-kernel-.patch
patch -p1 < 0003-usb-core-hub.c-Export-usb_port_suspend-because-phy-z.patch
patch -p1 < 0004-mmc-sdhci-add-quirk-for-broken-write-protect-detecti.patch
patch -p1 < 0005-Xillybus-drivers-in-the-kernel-tree-updated-to-match.patch
patch -p1 < 0006-Added-xillyvga-driver-to-kernel-tree.patch
patch -p1 < 0007-HP2-AXI-bus-width-set-to-32-bits-in-VGA-driver.patch
patch -p1 < 0008-Added-Xillybus-Lite-to-the-kernel.patch

Run menuconfig and tweak the kernel further, for instance I needed to enable RTL8188EU wireless chipset support under Staging drivers to get my USB dongle working. You probably want to add something to General setup -> Local version so once you install the kernel modules they won't overwrite the Xillinux kernel modules and in case of emergency you would still have to option to boot the older kernel:

make ARCH=arm menuconfig

1

Linux kernel source tree

2

The official Linux kernel from Xilinx

3

Linux Kernel Repository for Digilent FPGA Boards

Compiling on a PC

To compile the kernel I suggest using a x86 based laptop because compiling kernel on ZYBO itselt takes hours, besides since ZYBO does not have an hardware clock it could mess up the whole kernel compilation process. If you're on Ubuntu first install gcc-4.7-armhf-cross package. For Debian use Emdebian testing/unstable toolchain 4 and install the same package from there:

make  ARCH=arm UIMAGE_LOADADDR=0x8000 CROSS_COMPILE=arm-linux-gnueabihf- uImage modules -j32

If you already have Xilinx SDK installed you may want to use that instead to save some time:

source /path/to/Xilinx/SDK/2014.1/settings64.sh
make  ARCH=arm UIMAGE_LOADADDR=0x8000 CROSS_COMPILE=arm-xilinx-linux-gnueabi- uImage modules -j32

You can install the modules to a temporary directory as following:

make ARCH=arm INSTALL_MOD_PATH=/tmp/ modules_install

In ZYBO you probably want to mount the boot partition of SD card and keep a copy of working kernel:

mount /dev/mmcblk0p1 /boot
cp -v /boot/uImage /boot/uImage-$(uname -r)

Next step is to copy crosscompiled kernel and modules to ZYBO via ethernet cable:

scp arch/arm/boot/uImage  root@192.168.81.3:/boot/uImage
rsync -avz -e ssh /tmp/lib/modules/ root@192.168.81.3:/lib/modules/

Alternatively you just may copy them to root filesystem's /lib/modules directory.

If module dependency tracking is messed up you may want to run following on ZYBO:

depmod -a

4

Emdebian / Cross-development toolchains

Compiling on ZYBO

Compiling on ZYBO is of course more straightforward:

make UIMAGE_LOADADDR=0x8000 uImage modules -2
make modules_install
mount /dev/mmcblk0p1 /boot
cp -v /boot/uImage /boot/uImage-$(uname -r)
cp arch/arm/boot/uImage /boot/
reboot