1. Tizen Bootup

2. Contents Bootloader overview Tizen U-boot Tizen Systemd
Platform bootup

3. Bootloader

4. Tizen bootup overview Bootloader
Pass Machine ID and the boot arguments to kernel
Power on
ROM code
Booting device
Bootloader
Kernel
Platform

5. What is bootloader What is boot loader ? Why boot loader is needed ?
A boot loader is the first program which executes (before the main program i.e. kernel ) whenever a system is initialized
A boot loader is a computer program that loads the main program (i.e. operating system, kernel ) for the board after completion of the self-tests
Why boot loader is needed ?
Gives a development environment
Saves cost of flash writers
Give flexibility to load any operating system

6. Types of bootloader What are different types of boot loaders ?
Boot-ROM ( or Pre-Boot Loader)
Small code which loads First stage boot loader
First Stage Boot Loader
Small Piece of code that initialize the NAND/MMC & DRAM controller.
Second Stage Boot Loader
Primary function of the second-stage boot loader is to Loading the kernel into RAM or jumping directly to the start of the kernel.
Pre-Bootloader
First-Stage
Bootloader
Second-Stage
Bootloader
OS Kernel

7. U-boot loading process
Exynos4412
DRAM controller
DRAM
Cortex-A9
eSSD controller
Booting Device (NAND, MMC, SD, USB)
Internal ROM 1
iROM code
NAND controller
1st BL
2nd BL
SD/MMC controller
Internal SRAM 2 OS
UART/USB 3

8. U-boot loading process
BL0; iRom code (boot-rom or pre-boot loader)
Simple platform independent code, stored in internal ROM
Initialize basic functions (clock, stack, heap, etc)
Load first stage boot loader (from booting device to internal SRAM)
BL1; first boot loader
Simple platform independent code, stored in external memory(booting device)
Load second boot loader
Initialize NAND/MMC and DRAM controller
BL2; second boot loader
Platform dependent complex code, stored in external memory
Initialize clock, UART
Load OS image from booting device to DRAM
Jump to operating system

9. U-boot directory structure
api
Machine/arch independent API
examples
Example code for standalone applications
arch
Architecture specific files fs
Filesystem code (cramfs, ext2, jffs2, etc.)
board
Board dependent files
include
Header files
common
Misc architecture independent functions
lib
Files generic to all architectures
disk
Code for disk drive partition handling
net
Networking code
doc
Documentation
post
Power on self test
drivers
Commonly used device drivers
rtc
Real time clock drivers
tools
Tools to build S-Record or U-boot images

10. U-boot code sequence Disable all interrupts
Copy any initialized data from ROM to RAM
Zero the uninitialized data area
Allocate space for and initialize the stack
Initialize the processor’s stack pointer
Create and initialize the heap
Execute the initializers for all global data
Enable interrupts
Call main loop

11. U-boot code sequence Reset CPU and Hardware cpu/armv7/start.S _start()
Setup SP for Early Board Setup Environment (ASM->C)
Disable IRQ &FIQ Switch to supervisor mode
cpu/armv7/start.S reset()
General Relocation
arm/lib/crt0.S _main()
cpu/armv7/start.S relocate_code()
Early Board Setup
arm/lib/crt0.S board_init_f()
Low Level Initialization
Copy Binary to RAM
cpu_init_crit
Disable MMU
Invalidate and disable Instruction & data Cache
Calculate Addresses (SP, Dest, GD) for Relocation
Fix Relocation
Clear BSS
Setup SP for Common Board Setup
Setup GD and JUMP to Final Board Setup
lowlevel_init
arm/lib/crt0.S board_init_r()
board/samsung/lowlevel_init.S lowlevel_init()
Jump into main loop

12. U-boot code sequence _start() /* Entry point function */
reset() /* Reset CPU configurations */
save_boot_params() /* Save boot parameters */
Disable the FIQ & IRQ
Switch to supervisor mode
cpu_init_crit()
Invalidate I, D Cache
Disable I cache if CONFIG_SYS_ICACHE_OFF
Disable MMU
lowlevel_init()
_main() /* setup initial stack & global data And jump to C routine for board initialization */

13. U-boot code sequence board_init_f()
arch_cpu_init // basic arch cpu dependent setup
board_early_init_f // early board initialization, UART pin setting
timer_init // initialize timer
env_init // initialize mmc/sdcard environment
init_baudrate // initialize baudrate settings
serial_init // serial communication setup
console_init_f // stage 1 init of console, configure console from console.c
display_banner // say that we are here, print u-boot banner
print_cpuinfo // display cpu info
checkboard // display board info
init_func_i2c // initialize I2C
dram_init // configure available RAM backs
arm_pci_init

14. U-boot code sequence board_init_r()
board_init // setup chipselects specific configuration
logbuff_init_ptrs // initialize default log level
mem_malloc_init // configure malloc area
nand_init mmc_init // initialize flash/mmc
env_relocate // relocate environment or set NULL
stdio_init // setup stdio ready for use
api_init // initialize API
console_init_r // fully init console as a device
arch_misc_init // miscellaneous arch dependent initialization
misc_init_r // miscellaneous platform dependent initialization
interrupt_init // set up exceptions
enable_interrupts // enable exceptions
board_late_init // board late initialization
eth_initialize // setup ethernet
main_loop // jump to main loop & waiting for commands from console

15. U-boot code sequence main_loop() Wait for 3 seconds
Key pressed within 3 seconds
Input command
Command_mode()
Autoboot_mode()
boot()
loads()
tftpboot()
flash()
Jump to kernel image address

16. Loading through U-boot
SDRAM
Reset
CPU
Kernel
Root
File-System
Booting device
Bootloader
uboot
Bootloader
uboot
Kernel Image
Optional
compressed
Root File System

17. Loading through U-boot
Packing uImage
When the kernel is complied, mkimage attaches image_header to kernel image
Unpacking uImage
Magin number  CRC check  decompress  get board information  kernel booting
#define IH_MAGIC    0x /* Image Magic Number     */
#define IH_NMLEN    32 /* Image Name Length     */
typedef struct image_header {
uint32_t    ih_magic; /* Image Header Magic Number */
uint32_t    ih_hcrc; /* Image Header CRC Checksum */
uint32_t    ih_time; /* Image Creation Timestamp  */
uint32_t    ih_size; /* Image Data Size    */
uint32_t    ih_load; /* Data Load  Address   */
uint32_t    ih_ep; /* Entry Point Address       */
uint32_t    ih_dcrc; /* Image Data CRC Checksum   */
uint8_t     ih_os; /* Operating System         */
uint8_t     ih_arch; /* CPU architecture         */
uint8_t     ih_type; /* Image Type             */
uint8_t     ih_comp; /* Compression Type     */
uint8_t     ih_name[IH_NMLEN]; /* Image Name     */
} image_header_t;

18. start_kernel Architecture dependent setup
setup_arch() [/arch/arm/kernel/setup.c]
Exception(or trap) initialization
trap_init() [/arch/arm/kernel/trap.c]
Interrupt initialization
init_IRQ() [/arch/arm/kernel/irq.c]
sotfirq_init() [/kernel/sotfirq.c]
Scheduler initialization
sched_init() [/kernel/sched.c]
Timer initialization
time_init() [/arch/XXX/kernel/time.c]
Console initialization
console_init() [/driver/char/tty_io.c]
Module initialization
init_module() [/kernel/module.c]

19. start_kernel
Memory & System initialization , Cache & Buffer initialization , File system initialization
kmem_cache_init() [/mm/slab.c]
mem_init() [/arch/a,r/mm/init.c]
kmem_cache_size() [/mm/slab.c]
fork_init() [/kernel/fork.c]
proc_caches_init() [/kernel/fork.c]
vfs_caches_init() [/fs/dcache.c]
buffer_init() [/fs/buffer.c]
page_cache_init() [/mm/filemap.c]
signals_init() [/kernel/signal.c]
proc_root_init() [/fs/proc/root.c]
ipc_init() [/ipc/util.c]
init process creation
rest_init() [/init/main.c]

20. systemd

21. What is systemd? Sysvinit userspace launch (PID 1)
Only one process at a time running
Simply starting the system and then going to sleep until the next reboot
Systemd
Default init in Fedora 15 and later Leonard Poettering (2009)
improve the software framework for expressing dependencies
allow more processing to be done concurrently or in parallel during system booting
reduce the computational overhead of the shell.

22. What is systemd? Systemd in Tizen
System and service manager for tizen systemd
Ver. 43 (download
Parallelizes service execution
Socket and D-Bus activation for starting services and daemon
on-demand starting of daemons
Managing the service processes as a group using Linux cgroup
Supporting automount points
Snapshotting and restoring of services

23. systemd architecture

24. systemd architecture systemd Utility systemd target systemd daemon
monitoring and controlling systemd itself and its services
'systemctl' developers can query or send control commend to the systemd service manager
'systemd-journalctl' utility to see log message
systemd target
Tizen boot-up process is split up in various discrete steps and each step are grouped its unit using 'Target' unit to synchronize point
The boot-up process is highly parallelized in each target so that the order in which specific target units are reached in not deterministic
systemd daemon
system and service manager for Tizen platform
acts as init system
'systemd' daemonruns as user session with '--user' option
'systemd-journald' is a system service that collects and stores log data from the Kernel, from user processes via syslog or STDOUT/STDERR

25. systemd architecture systemd core systemd library & Linux Kernel
manages all units such as service, socket, mount and so on, stores all log data.
controlled by using systemd utility like 'systemctl'
systemd library & Linux Kernel
systemd requires to enable 'cgroup' and 'autofs' option in Kernel configuration
It also depends on dbus and some libraries such as libnotify, libudev

26. Platform bootup – sysinit.target
Early boot-up scripts
Most of file system are mounted and systemd related daemons are launched
basic.target
sysinit.target
multi-user.target
graphical.target
bootmode.target
Kernel
local-fs.target
swap.target
socket.target
-.mount
boot.mount
csa.mount
fsck-root.service
media.mount
opt-usr.mount
opt.mount
remount-rootfs.service
resize2fs-root.service
systemd-remount-api-vfs.service
var-run.mount
dev-hugepages.mount
dev-mqueue.mount
proc-sys-fs-binfmt_misc.automount
sys-fs-fuse-connections.mount
sys-kernel-config.mount
sys-kernel-debug.mount
sys-kernel-security.mount
systemd-ask-password-console.path
systemd-binfmt.service
systemd-journald.service
systemd-modules-load.service
systemd-random-seed-load.service
systemd-readahead-collect.service
systemd-readahead-replay.service
systemd-sysctl.service
systemd-tmpfiles-setup.service
dbus.socket
systemd-initctl.socket
systemd-journald.socket
systemd-shutdownd.socket
telnetd.socket
udev-control.socket
udev-kernel.socket

27. Platform bootup – basic.target
Basic boot-up
All necessary initialization for general purpose daemons are completed
basic.target
sysinit.target
multi-user.target
graphical.target
bootmode.target
Kernel
opt-var-kdb-db-libsqlfs.service
opt-var-kdb-db-smack-labels.service
smack-default-labeling.service
systemd-tmpfiles-clean.timer
tizen-debug-level.service
udev-trigger.service
udev.service
vconf-setup.service

28. Platform bootup – bootmote.target
Select boot mode
If kernel boot parameter has ‘charger_detect_boot’, the platform boots up as charging mode
basic.target
sysinit.target
multi-user.target
graphical.target
bootmode.target
Kernel
bootmode-charging.service
bootmode-graphical.service

29. Platform bootup – multi-user.target
Setup a multi-user system which is non-graphical support
Launching platform infrastructure daemons (such as dbus, power manager, gps manager, telephony daemon, WRT security daemon, media server, systemd-related daemons)
basic.target
sysinit.target
multi-user.target
graphical.target
bootmode.target
Kernel
alarm-server.service
avsystem.service
bluetooth-address.service
bluetooth-frwk-service.service
bluetooth.service
dbus.service
dlog-main.service
dlog-radio.service
getty.target
gps-manager.service
media-server.service
nfc-manager.service
power-manager.service
pulseaudio.service
secure-storage.service
sensor-framework.service
system-server.service
systemd-ask-password-wall.path
systemd-logind.service
systemd-user-sessions.service
telephony.service

30. Platform bootup – graphical.target
Setup a graphical environment
System user session for app privilege daemons such as Enlightenment (window manager)
Special target for middleware & mobile service
basic.target
sysinit.target
multi-user.target
graphical.target
bootmode.target
Kernel
core-efl.target
tizen-middleware.target
boot-animation.service
cbhm.service
e17.service
indicator.service
osp-app-service.service
quickpanel.service
scim.service
starter.path
xmodmap.service
xrdb.service
ac.service
calendar.service
contacts-service.service
download-provider.service
.service
msg-service.service
pushd.service
sound-server.service
tizen-mobile-session.target
wrt-preinstall-widgets.service
xorg.target
xorg.service

31. Systemd parsing

32. Platform bootup systemd
Control is moved from initramfs to systemd of Tizen platform
Run hardware init and fs mount, etc services
Bootup process run several units (.target)
Different target can be run in parallel
Many linux distributions adopt systemd as default
Red Hat Enterprise Linux, CentOS, Fedora, Arch Linux, openSUSE
Do not use daemon control script (/sbin/init, /etc/init.d/*, /etc/rc*.d)
/usr/lib/systemd
unit files: service, target, socket, device, mount, automount, path, snapshot, swap, timer
systemd utilities: systemctl, notify, analyze, cgis, cgtop, logictl, journalctl, nspawn

33. Platform bootup https://wiki.tizen.org/wiki/Porting_Guide entry point
.target vs .service
.target; service grouping
.service; process run

34. Parsing unit file – example (1/8)
/usr/lib/systemd/system
cat sysinit.target
target to parse

35. Parsing unit file – example (2/8)
Website
systemd download
manpage

36. Parsing unit file – example (3/8)
Can search all function and unit, configuration of systemd
enter target index

37. Parsing unit file – example (4/8)
target unit file

38. Parsing unit file – example (5/8)
Description on unit file option

39. Parsing unit file – example (6/8)

40. Parsing unit file – example (7/8)

41. Parsing unit file – example (8/8)
User awareness unit name = “System Initialization”
If emergency is running, wait
Run with local-fs.target, swap.target, sysinit.target.wants
Run after local-fs.target, swap.target, emergency.service, emergency.target
User can control service start and stop

42. Different Sessions
[Unit], [Service], [Install], [Socket], [Swap], [Mount], …
example; telephony.service
[Unit]; general options
unit name = Telephony daemon
Run after modem.service
[Service]; process options
Run telephony-daemon as main process
[Install]; actual work of unit excute
Create telephony.service symlink at multi-user.target.wants

43. References
systemd official Site
systemd FAQ (written by developer)