1. Beagle Board Fast Boot Hui Chen Keji Ren Dec 10 th, 2009 EE382N-4 Project

2. Outline Motivation Objectives Hardware of Beagle Board Techniques in optimizing boot time Boot time result Conclusions Future work Live demo EE382N-4 Project

3. Motivation: Why Faster Boot Time? Boot time definition: Time from turning on power to shell prompt (or a GUI). Impact the first perception an end user has of the product Critical to obtain a positive end user experience Save power EE382N-4 Project

4. Objectives Optimize software in Beagle Board for speed 1.bootloader 2.Linux Kernel 3.user-space applications Achieve a 5-second fast boot time in Beagle Board. Original boot time was about 15 seconds. EE382N-4 Project

5. Beagle Board Hardware OMAP 3530 Processor 600 MHz ARM Cortex-A8 with NEON 256MB on-chip RAM 256MB NAND Flash Peripheral I/Os DVI-D, SD/MMC+, S-Video, USB 2.0 Stereo In/Out, RS232 Serial Power USB or 5V DC EE382N-4 Project

6. Serial Cable Setup We made a customized Null Modem cable to connect Beagle Board to PC's serial port. EE382N-4 Project

7. Boot Sequence EE382N-4 Project

8. Strategies Load from NAND Flash X-loader and u-boot’s loading speed: NAND = 1MB, MMC = 500KB/s NAND’s block size is 128 KB per reading. We modified x-loader to only load 2 blocks (instead of 7 blocks originally). Remove unnecessary initialization, integration check and data movement We modified u-boot to 1. Embed configuration environments into u-boot (instead of reading from NAND) 2. Turn off Kernel CRC check 3. Remove Kernel relocation in u-boot EE382N-4 Project

9. Reduce user response time 1. Set bootdelay to zero in u-boot (so user can't interrupt u-boot) 2. Turn off serial output by passing 'quiet' parameter to Kernel Reduce code size We used '-Os -mthumb' flag to compile all code (x-loader, u-boot, kernel and user- space applications). Code size wins hands down. Remove unnecessary functionalities in Kernel and avoid modules We compiled a 1.2MB Kernel with USB, network, ext3/JFFS2 and a driver for our Pegasus Ethernet adapter. Strategies (cont.) EE382N-4 Project

10. User-space optimization 1. Tune uclibc and busybox carefully. Total size of rootfs is about 780KB without losing desired features. 2. Minimize init scripts: disable syslogd and klogd, remove unused tty and rc scripts. Choose faster file system Ext3 needs journal daemon whose loading time varies (can be over one second). Instead we use Ext2. We didn't choose JFFS2 on NAND due to the buggy Linux driver. Strategies (cont.) EE382N-4 Project

11. Boot Time Result [ 0.000005] Texas Instruments X-Loader 1.4.2 (Dec 8 2009 - 23:36:42) [ 0.003808] Loading u-boot.bin from nand [ 0.228279] [ 0.228349] [ 0.232136] U-Boot 2009.06-rc2-dirty (Dec 08 2009 - 23:47:30) [ 0.232178] [ 0.239877] OMAP3530-GP ES3.0, CPU-OPP2 L3-165MHz [ 0.239932] OMAP3 Beagle board + LPDDR/NAND [ 0.239959] DRAM: 256 MB [ 0.251298] NAND: 256 MiB [ 0.259473] In: serial [ 0.259526] Out: serial [ 0.259545] Err: serial [ 0.263444] Board revision C [ 0.263485] Hit any key to stop autoboot: 0 [ 0.267380] [ 0.271382] NAND read: device 0 offset 0x280000, size 0x123000 [ 1.551374] 1191936 bytes read: OK [ 1.555640] ## Booting kernel from Legacy Image at 80007fc0... [ 1.561426] Loading Kernel Image... OK [ 1.561455] OK [ 1.565348] [ 1.565392] Starting kernel... [ 1.565410] [ 1.895363] Uncompressing Linux.............................................................................. done, booting the kernel. [ 2.923280] Please press Enter to activate this console. Boot time was measured by using ptx_ts script from host Linux PC: $ picocom --b 115200 -d 8 /dev/ttyS0 | ptx_ts 'Texas' Total boot time from power on to terminal welcome prompt is 2.92 seconds without network. EE382N-4 Project

12. Boot time composition Delay (second) Loading u-boot from NAND0.22 Loading Kernel from NAND1.28 Execution (x-loader + u-boot)0.06 Uncompressing Kernel0.73 Execution (Kernel)0.29 Mounting Memory Card0.27 User-space applications0.07 Total2.92 EE382N-4 Project

13. Conclusions We achieved shorter boot time than we expected. A project page has been setup with wiki pages and all source codes: http://code.google.com/p/swiftbeagle/ We obtained a good understanding on 1.Beagle Board hardware 2.What are required in writing a bootloader (such as disabling MMU/dcache, detecting machine ID and passing ATAGS to Kernel). We wrote our own bootloader called S-Loader. However, development of S-Loader is still in debugging phase and Kernel stalls after uncompressing itself. 3.Patching Kernel source 4.Building a Linux rootfs from scratch 5.Compiler optimization techniques (we believe we found a defect in Code Sourcery's latest ARM gcc compiler/library) EE382N-4 Project

14. Future Work: What Would Be Different? 0.5 second boot can be realized by utilizeing: XIP(Execution in Place), uncompressed Kernel and faster FS(JFFS2 on MTD). EE382N-4 Project

15. Demo Time EE382N-4 Project