Configure FPGA/SPI Flash to Run Linux on LX9 MicroBoard, Part 1 – Preparation

This is Part 1 for the topic, to prepare configuration data for LX9 MicroBoard.

The FPGA design is done with ISE 13.2 based on AXI/Little Endian MicroBlaze 8.20a. The details were presented here at Run Linux on Avnet Spartan-6 LX9 MicroBoard.

The Linux kernel is built with Petalinux SDK 2.1. You may contact PetaLogix to obtain a license and SDK to try out. If you prefer Xilinx’s embedded Linux solution, you can find useful information from its Open Source Wiki. From configuration point of view, it makes no difference which one is used.

The keys to prepare the configuration data are:

• understand how SPI Flash is partitioned
• understand how each partition is used
• make sure proper sizes for partitions, especially for the partition where Linux is at

You may need build kernel more than once, if you don’t know the kernel size beforehand. For example in the second build, you can adjust partitions to fit Linux into flash.

Here’s Flash partitions used by Petalinux, and sizes are modified because of 11MB kernel. Note SPI Flash on the MicroBoard has 256 64KB blocks, total space is 16MB.

Partition	Name	Size (blocks)	Flash Address	Usage
0	fpga	2MB (32)	0x0	bitstream and fs-boot
1	boot	256KB (4)	0x200000	u-boot
2	bootenv	128KB (2)	0x240000	u-boot environment variables (not used here)
3	config	128KB (2)	0x260000	used by flatfsd to store persistent data, required but not used by configuration
4	image	12.5MB (200)	0x280000	Linux kernel and filesystem
5	spare	1MB (16)	0xf00000	remaining space (not used here)

Here’s how partitions are specified in kernel configuration (System Settings -> Flash Partition Table -> Image Partition Size).

System Settings

Flash Partition Table

Image Partition Size

Once the kernel is rebuilt, along with the outputs of FPGA bitstream from ISE/EDK, and U-Boot from XSDK, the following files are used to construct configuration data, and/or bootstrap Linux:

File	Description	Built by	Usage
system_bd.bmm	BRAM memory map	ISE/XPS	to generate download.bit by script d2m
mb_system_top.bit	design bitstream
fs-boot_0.elf	fs-boot	XSDK
u-boot.elf	u-boot executable	Petalinux SDK	not used by configuration, but useful to transfer images to Flash
u-boot-s.bin	u-boot relocatable binary		to generate sopc_lx9.mcs by script pgen.ub
image.ub	Linux kernel and filesystem binary

This is the script d2m, a wrapper of data2mem:

d2m

#!/bin/sh data2mem \ -bm mb_system_bd.bmm \ -p xc6slx9csg324-2 \ -bt mb_system_top.bit \ -bd fs-boot_0.elf \ tag microblaze_0 \ -o b download.bit

This is the script pgen.ub, an wrapper of promgen:

pgen.ub

#!/bin/sh promgen -w \ -p mcs \ -c FF \ -o sopc_lx9 \ -s 16384 \ -u 0000 download.bit \ -data_file up 200000 u-boot-s.bin \ -data_file up 280000 image.ub \ -spi

The following capture summarizes the procedure to generate configuration data.

Generate Configuration Data

If you would rather prepare PROM from iMPACT GUI, here’re the steps (Note, the files could be at any folder).
Launch iMPACT and select “Prepare a PROM File”.

Prepare PROM File

Select and Enter as following (highlighted).

Prepare PROM Steps

Add device bitstream.

Add Device Bitstream

Add 2 data files.
The first one is U-Boot, and make sure it is at proper address on Flash, in this case it is 0x200000.

U-Boot Flash Address

Add U-Boot

The second data file is Linux kernel and filesystem. Make sure the Flash address is set to 0x280000.

Kernel Flash Address

Add Kernel

Here’s the resulting data file assignment.

Data File Assignment

Proceed to generate configuration data.

Generate File

You can find scripts and source data files from here.

As a side note, when people move to high end FPGA solutions with processor integration, as Xilinx calls Zynq as EPP (Extensible Processing Platform), and Altera calls SoC FPGA with HPS (Hard Processor System), there is less or no need, in a sense, to configure FPGA from persistent storage such as Flash. The processor can easily make bitstreams and software images available to FPGA.
For large volume and low cost applications, soft-cores such as MicroBlaze and Nios are good solutions, and configuration is still needed.

Configure FPGA/SPI Flash to Run Linux on LX9 MicroBoard, Part 3 – Easy Way

This is Part 3 for the topic.
In Part 2 – Quick Way, network connection and tftp server, plus certain knowledge of U-Boot are needed. You can avoid them by just using iMPACT to program the FPGA/SPI Flash. Here’s how.

On the host with Xilinx design tools installed, navigate to the folder with following files.

File	Description	Usage
sopc_lx9.mcs	configuration data	program FPGA/SPI Flash
impact.cmd	programming script	for Xilinx USB II cable (6MHz)
impact.12Mh.cmd	programming script	for Xilinx USB II cable (12MHz)
impact.onboard.cmd	programming script	for Digilent Onbard JTAG

Program FPGA/SPI Flash by running iMPACT in batch mode.

USB II Batch Program

The Linux kernel and u-boot has a size about 10MB (still have some rooms left for 16MB Flash, I could see many potentials there), and FPGA/fs-boot has only 336KB. The final MCS data triples the size (in ASCII format).
It takes about 68 minutes on my Linux host, including verification. Program alone may take about 43 minutes, by using default JTAG clock speed, 6MHz.

USB II Program Done

With impact.12Mh.cmd, it takes about 35 minutes. iMPACT complains 24MHz is not supported.

Program at 12MHz

I also tried several times to program by using MicroBoard’s Onboard USB/JTAG. It is supposed to be running fast (in 15MHz?). By 1) modifying Avnet Tom’s script listed in LX9 board forum Remarks on AvtS6LX9MicroBoard_SW302_PetaLinux, and 2) by iMPACT GUI, but I was never able to go to the end. I remembered once I let it run overnight from GUI, it was less than half way through in the next morning, and I had to abort the process.
It could be I didn’t specify options correctly. I attach the programming script for Onboard JTAG, just for reference, but be warned, don’t try it, it may take forever to program.

If you’re more interested at programming through iMPACT GUI to have a good understanding what’s going on, here’re some screenshots.

Start iMPACT by choosing “Configure devices using Boundary-Scan (JTAG)”.

Configure Devices

Select “No” for “Auto Assign Configuration Files Query Dialog”.

No for Auto Assign

Right click the device from “Boundary Scan” tab to add SPI Flash.

Add SPI Flash

Select attached SPI Flash (N25Q128 1.8/3.3V).

Select SPI Flash

Right click added SPI Flash device and select “Program”.

Program

It achieves identical result as running the script in batch mode, and takes about the same time to finish.

If you’re interested, here’s the link for scripts and configuration data.

Configure FPGA/SPI Flash to Run Linux on LX9 MicroBoard, Part 2 – Quick Way

This is Part 2 for the topic, I will present Part 1 (Preparation) after Part 3 (Easy Way) is done.

Petalinux is using a 2-stage booting process. The First Stage boot, FS-Boot, is running from FPGA’s BRAM once powered on. It’s sole responsibility is to load the main system bootloader, i.e., U-Boot, from the flash to the larger external memory, and run U-Boot from the external memory.

One of the quick ways to configure FPGA is to copy binary images to the flash, instead of programming it, which could take significant time depends on programmer used.

In order to do that, networking connectivity and a mechanism to deliver and retrieve images are required.
As used by almost everyone, I’m using tftp. The host runs tftpd is connected to the LX9 MicroBoard via a router.

The following images are needed.

Image	Description	Usage
download.bit	bitstream plus fs-boot binary	FPGA and fs-boot image on flash
u-boot.elf	U-Boot in ELF format	to transfer u-boot-s.bin and image.ub to flash
u-boot-s.bin	relocatable U-Boot in binary format	U-Boot on flash
image.ub	Linux kernel and root filesystem in binary format	Linux on flash
impact.cmd	script for impact (not required)	transfer download.bit
xmd.ini	script for xmd (not required)	run u-boot.elf

I am using Platform Cable USB II programmer, usb/uart port is directly connected to the host via minicom.

Board Connection

Start tftp daemon, and point the working folder to where the above files are.

Start tftp

Next step is to program FPGA through impact. If you’re using Digilent’s HS1 or onboard JTAG connection, your script should be different.

Program FPGA

Then download and run U-Boot through xmd. If you’re using Digilent’s HS1 or onboard JTAG connection, your script should be different.

Download and Run U-Boot

If the flash is programmed already, stop the autoboot process from the uart port console, in order to move new U-Boot and Linux to the flash.

Stop Autoboot

Now it is time to copy Linux kernel and U-Boot to flash. But before doing that, IP addresses for the tftp server (host) and the board (target) need be set. Your IP addresses could be different the ones used below.
Here’s how to do it and copy the Linux kernel (image.ub) to the flash.

IP Setup and Copy Kernel

Then copy the U-Boot.

Copy U-Boot

Now if everything goes well, you can run Linux by either hitting the reset button or issuing boot command from U-Boot prompt.

Booting

Here’s the booted console, and SPI flash’s partitions.

Booted Console and SPI Flash Partitions

You can find listed binary images and scripts here.