Download as PDF, PPTX
![Boot Sequence
start
arch/arm/boot/ start
compressed/
head.S start_kernel
arch/arm/kernel/
head.S
bootstrap loader init/main.c
(uncompress)
ARM-specific
kernel code
kernel code
detail boot sequence is listed in [9]](https://image.slidesharecdn.com/linux-090422224346-phpapp01/85/Linux-Porting-7-320.jpg)
![Kernel Porting – I/O Memory Map
static struct map_desc foo_io_desc[] __initdata =
{
{
/* address after mapping */
.virtual = IO_ADDRESS(CPU_DEV_PHY_BASE),
/* page index of physical address */
.pfn = __phys_to_pfn(CPU_DEV_PHY_BASE),
.length = CPU_DEV_IO_LEN, /* address mapping range */
.type = MT_DEVICE /* I/O type */
},
……
};
….
static void __init foo_map_io(void)
{
iotable_init(foo_io_desc, ARRAY_SIZE(foo_io_desc));
}](https://image.slidesharecdn.com/linux-090422224346-phpapp01/85/Linux-Porting-17-320.jpg)
![Boot Sequence
start
arch/arm/boot/ start
compressed/
head.S start_kernel
arch/arm/kernel/
head.S
bootstrap loader init/main.c
(uncompress)
ARM-specific
kernel code
kernel code
detail boot sequence is listed in [9]](https://image.slidesharecdn.com/linux-090422224346-phpapp01/75/Linux-Porting-7-2048.jpg)
![Kernel Porting – I/O Memory Map
static struct map_desc foo_io_desc[] __initdata =
{
{
/* address after mapping */
.virtual = IO_ADDRESS(CPU_DEV_PHY_BASE),
/* page index of physical address */
.pfn = __phys_to_pfn(CPU_DEV_PHY_BASE),
.length = CPU_DEV_IO_LEN, /* address mapping range */
.type = MT_DEVICE /* I/O type */
},
……
};
….
static void __init foo_map_io(void)
{
iotable_init(foo_io_desc, ARRAY_SIZE(foo_io_desc));
}](https://image.slidesharecdn.com/linux-090422224346-phpapp01/75/Linux-Porting-17-2048.jpg)
Uploaded byChamp Yen
Linux Porting
This document provides an overview of porting Linux to a new ARM platform. It discusses setting up the GNU toolchain, kernel prerequisites and configuration, creating machine-specific files and code, initializing drivers and boot options. Key steps include registering the new machine, adding architecture-specific code and configuration files, initializing I/O mapping and IRQs, and creating an initramfs image to test bootability. References for further information on ARM Linux boot sequences and porting are also provided.
In this document
Powered by AI
Introduction to Linux porting for ARM platforms, outlining the GNU toolchain and key components.
Details on various GNU toolchains including CodeSourcery and Buildroot for ARM platform setup.
Kernel prerequisites such as DRAM initialization and memory mapping images are detailed.
Overview of boot sequence, memory maps, and directory structure required for ARM kernel porting.
Procedures to register new machines, including configuration and Makefile modifications.
Initial kernel setup procedures, I/O memory mapping, and interrupt request configurations.
Focus on timer configuration and DMA memory handling procedures in ARM kernel.
Kernel boot options, ATAG lists for dynamic booting, and registering device drivers for ARM.
Comparison between initrd and initramfs in terms of structure and usage, including debugging techniques.
List of references for further reading and a Q&A session.
More Related Content
Linux Porting
- 1. Linux Porting for newARM platform Champ Yen http://champyen.blogspot.com champ.yen@gmail.com
- 2. OutLine GNU Toolchain Linux KernelPrerequisites and Assumptions Images Boot Sequence Kernel Configuration & Compilation Kernel Porting Device Drivers Boot Options initramfs vs initrd References
- 3. GNU Toolchains CodeSourcery gnu toolchain http://www.codesourcery.com/sgpp/lite/arm/download.html Buildroot http://buildroot.uclibc.org/ Scratchbox http://www.scratchbox.org/ OpenEmbedded http://wiki.openembedded.net/index.php/Main_Page Ptxdist http://www.pengutronix.de/software/ptxdist/index_en.html
- 4. GNU Toolchains -buildroot linux kernel like configuration interface ncurse UI, .config file uClibc generate linux 2.6 compatible small footprint applications for most platform remember to enable software float output: toolchain/uClibc/busybox/rootfs
- 5. Linux Kernel Prerequisitesand Assumptions DRAM is initialized Hardware-related initialization tasks are done MMU/Cache is disabled specific values should be saved in registers r1: Machine ID, r2: pointer of ATAG list (optional)
- 6. Images and intermediatefiles piggy.o image vmlinuz objcopy (binary gzip piggy.gz asm (ELF object) object) misc.o compressed head.o stripped image binary kernel binary kernel bootable kernel image kernel proper (zImage)
- 7. Boot Sequence start arch/arm/boot/ start compressed/ head.S start_kernel arch/arm/kernel/ head.S bootstrap loader init/main.c (uncompress) ARM-specific kernel code kernel code detail boot sequence is listed in [9]
- 8. Kernel Porting –Kernel Memory Map 0xFFFF_FFFF CPU vector page/copy_user_page(),clear_user_page() 0xFFFF_0000 DMA memory mapping 0xFF00_0000 free for platform use VMALLOC_END vmalloc()/ioremap() space VMALLOC_START kernel direct-mapped RAM region PAGE_OFFSET kernel module space TASK_SIZE user space mapping 0x0000_1000 CPU vector page/null pointer trap 0x0000_0000
- 9. Kernel Porting –Directories mm/ memory-handling related code boot/ bootstrap loader code kernel/ ARM architecture dependent code mach-XXXXXX/ specific machine dependent code configs/ each machine’s default kernel configurations
- 10. Kernel Porting –new machine items refer to other machine to create or modify items(ex: foo, fxx) register the new machine arch/arm/tools/mach-types Create machine folder arch/arm/mach-fxx arch/arm/mach-fxx/include/mach Modify or Create Kconfig & Makefile arch/arm/Kconfig (usually add config ARCH_FXX for architecture) arch/arm/Makefile arch/arm/mm/Kconfig arch/arm/mach-fxx/Kconfig (config MACH_FOO for machine) arch/arm/mach-fxx/Makefile arch/arm/mach-fxx/Makefile.boot (set zreladdr-y for image location)
- 11. Kernel Porting –new machine items register the new machine Add an entry in arch/arm/tools/mach-types ex: foo MACH_FOO FOO 65535 For official registration, should register here, also. http://www.arm.linux.org.uk/developer/machines/
- 12. Kernel Porting –new machine items create machine folders arm/arch/mach-fxx for machine dependent source code arm/arm/mach-fxx/include/mach for machine dependent headers/assembly debug-macro.S: adduart, senduart, busyuart, waituart dma.h entry-macro.S: macro get_irqnr_and_base hardware.h system.h: arch_idle(), arch_reset() io.h timex.h: CLOCK_TICK_RATE irqs.h: NR_IRQS uncompress.h: putc() memory.h: PHYS_OFFSET vmalloc.h: VMALLOC_END
- 13. Kernel Porting –new machine items modify or create Kconfig & Makefile arch/arm/Kconfig config ARCH_FXX bool “FXX family processors“ help This enables support for systems based on the fxx processors. ……… source "arch/arm/mach-fxx/Kconfig" arch/arm/Makefile machine-$(CONFIG_ARCH_FXX) := fxx arch/arm/mm/Kconfig (ex: ARM926-based) config CPU_ARM926T bool "Support ARM926T processor" depends on ARCH_INTEGRATOR || ARCH_VERSATILE_PB || … || ARCH_FXX default y if ARCH_VERSATILE_PB || ARCH_VERSATILE_AB || … || ARCH_FXX
- 14. Kernel Porting –new machine items modify or create Kconfig & Makefile arch/arm/mach-fxx/Kconfig menu "FXX platform type“ depends on ARCH_FXX config MACH_FOO bool "Support FOO platform" default y help Include support for the FOO platform. endmenu arch/arm/mach-fxx/Makefile # Common support (must be linked before board specific support) obj-y := architecture depend code # Specific board support obj-$(CONFIG_MACH_FOO) += core.o machine depend code arch/arm/mach-fxx/Makefile.boot zreladdr-y := 0x01008000
- 15. Kernel Porting –description structure MACHINE_START(FOO, "FOO processor") /* Maintainer: Champ Yen */ .map_io = foo_map_io, .init_irq = foo_init_irq, .init_machine = foo_init, .timer = &foo_timer, /* for ATAG list is optional */ .boot_params = 0x01000100, MACHINE_END
- 16. Kernel Porting –Initialization code I/O Memory Mapping Table IRQ Timer struct sys_timer Initial order: .map_io .initrq .timer .init_machine
- 17. Kernel Porting –I/O Memory Map static struct map_desc foo_io_desc[] __initdata = { { /* address after mapping */ .virtual = IO_ADDRESS(CPU_DEV_PHY_BASE), /* page index of physical address */ .pfn = __phys_to_pfn(CPU_DEV_PHY_BASE), .length = CPU_DEV_IO_LEN, /* address mapping range */ .type = MT_DEVICE /* I/O type */ }, …… }; …. static void __init foo_map_io(void) { iotable_init(foo_io_desc, ARRAY_SIZE(foo_io_desc)); }
- 18. Kernel Porting –IRQ arch/arm/mach-fxx/include/mach/entry-macro.S get_irqnr_and_base: after calling irqnr: irq number, not equal condition should be set. arch/arm/mach-fxx/include/mach/irqs.h NR_IRQS (number of irq types) should be defined struct irq_chip, irqaction set_irq_chip(), set_irq_flags(), set_irq_handler(), setup_irq() ……… static struct irq_chip foo_irq_chip = { for(i = o; i < NR_IRQS; i++){ .ack = foo_int_ack, set_irq_handler(i, handle_level_irq); .mask = foo_int_mask, set_irq_chip(i, &foo_irq_chip); .unmask = foo_int_unmask, set_irq_flags(i, IRQF_VALID); }; } ………
- 19. Kernel Porting -Timer struct sys_timer foo_timer = { .init = foo_timer_init, .offset = foo_gettimeoffset, };
- 20. Kernel Porting –DMA memory (optional) Influence to dma_alloc_coherent() usage In arch/arm/mach-fxx/include/mach/dma.h MAX_DMA_ADDRESS In arch/arm/mach-fxx/include/mach/memory.h CONSISTENT_DMA_SIZE ISA_DMA_THRESHOLD
- 21. Boot Options –static string Boot options -> Default kernel command string ex: mem=8M@0x01000000 initrd=0x01180000,145762
- 22. Boot Options –ATAG lists ATAG provides dynamic boot option passing There are two way to pass pointer of ATAG lists r2 value passed by bootloader, .boot_params in machine descriptor refer to arch/arm/include/asm/setup.h struct tag_header { __u32 size; ATAG_CORE __u32 tag; }; …… struct tag { struct tag_header hdr; union { struct tag_core core; struct tag_mem32 mem; … } u; ATAG_NONE };
- 23. Device Drivers platform_device_register(), platform_driver_register() for some on-chip devices(ex: clock/power control) UART subsystem in driver/serial for startup message, console ,and shell Framebuffer subsystem in driver/video
- 24. initramfs vs initrd initrd initramfs image ext2 image + gzip cpio + gzip implementation block device tmpfs first execution /linuxrc /init mount rootfs pivot_root switch_root initrd requires ext2 and block devices support. It adds 150KB+ to kernel size.
- 25. initramfs create an initramfs image by command: find . | cpio -o -H newc | gzip > ../initramfs.cpio.gz take care of the distance between image and kernel, otherwise image will be overwritten by kernel. /init ex: #!/bin/busybox sh #/bin/busybox --install mount -t proc proc /proc exec /bin/busybox sh
- 26. Debug decompression: putc() definiition in include/mach/uncompress.h kernel debugging features in kernel hacking of kernel options (and CONFIG_DEBUG_LL option for low level debugging) early debug: printascii/printhex(2,4,8) make use of uart macros in include/mach/debug-macro.S printk() CONNFIG_KGDB
- 27. References Embedded Linux Primer, Christopher Hallinan, Prentice Hall Building Embedded Linux Systems 2/e, Karim Yaghmour, Oreilly linux-2.6.2x-xx/Documentation/arm http://heaven.branda.to/~thinker/GinGin_CGI.py/get_afile/166/porting_to_arm.pdf http://www.glomationinc.com/PortingLinuxKernel.pdf http://www.ens-lyon.fr/LIP/Pub/Rapports/RR/RR2006/RR2006-08.pdf http://glt08.linuxtage.at/slides/glt08-kvas_linuxonarm.pdf http://www.linux-arm.org/LinuxKernel/LinuxNewPlatformPort http://gicl.cs.drexel.edu/people/sevy/linux/ARM_Linux_boot_sequence.html http://www.simtec.co.uk/products/SWLINUX/files/booting_article.html http://www.ibm.com/developerworks/linux/library/l-initrd.html http://blog.linux.org.tw/~jserv/archives/001954.html
- 28.