Embedded Linux Conference Europe Sascha Hauer

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1 Embedded Linux Conference Europe 2012 Sascha Hauer Slide 1 - Pengutronix

2 Agenda Tour through barebox Devicetree Multiplatform Bootloader barebox live demo Slide 2 - Pengutronix

3 Tour through barebox Basic hardware initialization (SDRAM, clocks) Startup User Interface Start operating system Update Initial hardware bringup Slide 3 - Pengutronix

4 What does a bootloader need? Motivation - A bootloader should: be configurable be scriptable have a maintainable codebase have a driver model have real filesystem support not require people to know memory layout of a board be able to see every type of device as a file be able to start itself second stage Slide 4 - Pengutronix

5 barebox Busybox The swiss army knife of embedded Linux Barebox The swiss army knife for bare metal Slide 5 - Pengutronix

6 barebox barebox Started as U-Boot-v2 in July 2007 as a fork of U-Boot Renamed to barebox in December 2009 Evolves with ~140 commits / month - 92 boards - 8 architectures: ARM, Blackfin, Mips, Nios2, Openrisc, sandbox, X86 Slide 6 - Pengutronix

7 Kconfig From basic SRAM config to full blown barebox without touching code Slide 7 - Pengutronix

8 Lowlevel init Setup the minimum requirements for barebox, not more Usually this means setting up SDRAM Ideally this would be the only board specific code Often written in assembly Barebox allows to write this code in C Optionally reset vector is under board control Slide 8 - Pengutronix

9 Initcalls / driver model Barebox starts up using initcalls Board / SoC code registers devices Drivers probe based on devices found Heavily inspired by Linux Kernel driver model Slide 9 - Pengutronix

10 User interface Autoboot based on Informations from the SoC Console Menu Input devices LEDs Slide 10 - Pengutronix

11 Menu support The menu can be instantiated from C or the commandline Allows executing arbitrary commands / scripts from menu items shell for experts, menu for convenience and occasional user Slide 11 - Pengutronix

12 Loading Kernel From: TFTP, NFS (SPI) NOR flash, NAND flash SD/MMC UART USB Mass Storage FAT UBI All accessible as files Slide 12 - Pengutronix

13 Starting Kernel barebox has a single boot command supporting zimages uimages barebox images devicetrees initrd files Slide 13 - Pengutronix

14 Booting: fast ARM needs the MMU for datachaches, so barebox has generic MMU support for ARM The block layer has a LRU caching mechanism Autoboot timeout 0 still allows interruption Slide 14 - Pengutronix

15 Updating Update strategies are project specific Scripting 'cp' command Building blocks for a project specific update conept Slide 15 - Pengutronix

16 Hardware bringup gpio_* md mw Memcpy, memset, memcmp Tab completion magicvar clk_dump time devinfo clk_* filetype iomem Slide 16 - Pengutronix

17 barebox in 128Kb Freescale i.mx51 babbage - Networking support with tftp, dhcp, ping and dns - MMC/SD read/write support - FAT read/write support - Stack unwinding - Kallsyms - Almost full command set Phytec i.mx27 pcm038 - Networking support with tftp, nfs, dhcp, ping and dns - CFI NOR flash support - NAND flash support - Stack unwinding - Almost full command set Slide 17 - Pengutronix

18 barebox in 128Kb TI OMAP3 BeagleBoard - Networking support with tftp, ping dhcp, dns - USB support - USB network adapter support - NAND support - MMC/SD support - FAT read/write support - Almost full command set TI OMAP3 BeagleBoard xload config (33k) - NAND support (ro) - MMC/SD (ro) - FAT support - Noninteractive build Slide 18 - Pengutronix

19 Devicetree support Unlike PC hardware SoCs are not discoverable Before the devicetree migration the hardware description was in C-Code inside the Kernel. That's what barebox still does Using devicetrees allows separation of the hardware description from the code Using devicetrees is becoming the standard way to start the kernel on ARM, PowerPC and other architectures Slide 19 - Pengutronix

20 Devicetree The devicetree has to be written for every new board anyway - Let's use it for barebox aswell Slide 20 - Pengutronix

21 Devicetree Binary blob (dtb) Slide 21 - Pengutronix

22 Devicetree Unflatten tree Slide 22 - Pengutronix

23 Devicetree now with devicetree Common code devicetree Board specific code startup code Slide 23 - Pengutronix

24 Devicetree Separate code from board data Make binaries more universally usable By using devicetrees we can reuse the same Kernel binary for different hardware variants Slide 24 - Pengutronix

25 Towards a multiarch bootloader now with devicetree multiarch Common code devicetree Board specific code startup code Slide 25 - Pengutronix

26 Multiplatform multiarch Barebox update handler Boot device Slide 26 - Pengutronix

27 Multiplatform (replace barebox with kernel) Linux Common code startup code devicetree Slide 27 - Pengutronix

28 Livedemo Now for the demo... Slide 28 - Pengutronix

29 Thank you very much website: IRC: #barebox Project Mailing List: Sascha Hauer Slide 29 - Pengutronix

30 Automount support Allows to automatically detect and mount devices when first accessed Allows to probe devices only when they are needed First, add automountpoint: # automount /mnt/tftp 'ifup eth0 && \ mount -t tftp \ $eth0.serverip /mnt/tftp' Then, simply access files, barebox will mount in the background: # cp /mnt/tftp/zimage /zimage Slide 30 - Pengutronix

Booting Linux Fast & Fancy. Embedded Linux Conference Europe Cambridge, Robert Schwebel

Booting Linux Fast & Fancy. Embedded Linux Conference Europe Cambridge, Robert Schwebel Booting Linux Fast & Fancy Embedded Linux Conference Europe Cambridge, 2010-10-28 Robert Schwebel Slide 1 - http://www.pengutronix.de - 01/11/2010 Motivation: Booting Linux