Replicant

== Introduction ==

This page contains information on how to work on a bootloader replacement.

== Informations ==

 * The [http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary official u-boot source code] already has support for the S5PC110 SOC(system on a chip) that the Nexus S uses

 * The S5PC110 has a bootrom

 * The Nexus S has an usb port with an FSA9480 behind it

=== Partitioning informations ===

Here's a detailed output showing the partitioning of the NAND that you can obtain with {{{ heimdall print-pit }}} with the device in download mode (VOL+ and VOL- held at reboot):

{{{

Entry Count: 16

Unknown 1: 0

Unknown 2: 0

Unknown 3: 0

Unknown 4: 0

Unknown 5: 0

Unknown 6: 0

Unknown 7: 0

Unknown 8: 0

--- Entry #0 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 0

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 1

Unknown 2: 0

Unknown 3: 0

Partition Name: IPBL

Filename: bootloader.img

--- Entry #1 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 1

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 7

Unknown 2: 0

Unknown 3: 0

Partition Name: SBL

Filename: 

--- Entry #2 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 2

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 7

Unknown 2: 0

Unknown 3: 0

Partition Name: SBL2

Filename: 

--- Entry #3 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 3

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 4

Unknown 2: 0

Unknown 3: 0

Partition Name: PARAM

Filename: 

--- Entry #4 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 4

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 5

Unknown 2: 0

Unknown 3: 0

Partition Name: MISC

Filename: 

--- Entry #5 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 5

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 32

Unknown 2: 0

Unknown 3: 0

Partition Name: BOOT

Filename: boot.img

--- Entry #6 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 6

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 32

Unknown 2: 0

Unknown 3: 0

Partition Name: RECOVERY

Filename: recovery.img

--- Entry #7 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 7

Partition Flags: 1 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 1878

Unknown 2: 0

Unknown 3: 0

Partition Name: CACHE

Filename: cache.img

--- Entry #8 ---

Unused: Yes

Partition Type: 0 (RFS)

Partition Identifier: 8

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 54

Unknown 2: 0

Unknown 3: 0

Partition Name: RADIO

Filename: radio.img

--- Entry #9 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 9

Partition Flags: 1 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 27

Unknown 2: 0

Unknown 3: 0

Partition Name: EFS

Filename: 

--- Entry #10 ---

Unused: No

Partition Type: 0 (RFS)

Partition Identifier: 10

Partition Flags: 0 (R)

Unknown 1: 0

Partition Block Size: 256

Partition Block Count: 1

Unknown 2: 0

Unknown 3: 0

Partition Name: DGS

Filename: dgs.img

--- Entry #11 ---

Unused: No

Partition Type: 2 (EXT4)

Partition Identifier: 0

Partition Flags: 2 (R/W)

Unknown 1: 0

Partition Block Size: 512

Partition Block Count: 2048

Unknown 2: 0

Unknown 3: 0

Partition Name: PGPT

Filename: emmc.img

--- Entry #12 ---

Unused: No

Partition Type: 2 (EXT4)

Partition Identifier: 1

Partition Flags: 2 (R/W)

Unknown 1: 0

Partition Block Size: 512

Partition Block Count: 1048576

Unknown 2: 0

Unknown 3: 0

Partition Name: SYSTEM

Filename: system.img

--- Entry #13 ---

Unused: No

Partition Type: 2 (EXT4)

Partition Identifier: 2

Partition Flags: 2 (R/W)

Unknown 1: 0

Partition Block Size: 512

Partition Block Count: 2097152

Unknown 2: 0

Unknown 3: 0

Partition Name: USERDATA

Filename: userdata.img

--- Entry #14 ---

Unused: No

Partition Type: 2 (EXT4)

Partition Identifier: 3

Partition Flags: 2 (R/W)

Unknown 1: 0

Partition Block Size: 512

Partition Block Count: 33554432

Unknown 2: 0

Unknown 3: 0

Partition Name: MEDIA

Filename: media.img

--- Entry #15 ---

Unused: No

Partition Type: 2 (EXT4)

Partition Identifier: 4

Partition Flags: 2 (R/W)

Unknown 1: 0

Partition Block Size: 512

Partition Block Count: 33

Unknown 2: 0

Unknown 3: 0

Partition Name: SGPT

Filename: 

}}}

== Serial Console ==

It is possible to setup a serial console on the Nexus S. It will show:

 * the 1st bootloader output

 * the 2nd bootloader output

 * the 2nd bootloader #2 output

 * the fiq debugger

 * (the kernel output if enabled)

=== How to enable serial console ===

 * completely turn off the Nexus S

 * attach the microUSB connector to the Nexus S

 * wire GND and ID (from the microUSB connector) to a 150K resistor

 * get an UART to USB module like this one: http://www.dealextreme.com/p/usb-to-uart-5-pin-cp2102-module-serial-converter-81872

 * wire it following this table:

|| UART to USB board output || resistor || microUSB connector(s) name(s) || microUSB wire color ||

|| N/A || 150K Ohm || ID and GND || ID not wired (the 5th connector that is unused), GND is black ||

|| 3.3V || N/A || V+ || red ||

|| GND || N/A || GND || black ||

|| Rx || N/A || D- || white ||

|| Tx || N/A || D+ || green ||

'''Warning: the voltage to use is 3.3V and not 5V! Using 5V can cause serious damages to the UART component.'''

When the USB to UART module is connected to the host PC, a new tty node will be created on the host PC, usually {{{ /dev/ttyUSB0 }}}. 

To read/write on the serial, you can use screen (or picocomm, or any other software that deals with serial consoles):

{{{ screen /dev/ttyUSB0 115200 }}}

115200 is the baud rate to use (certainly with most UART to USB board). 

Photos: here's what it looks like when all setup:

Then, do a regular boot. You should see the second bootloader #2 output. To get the 1st and 2nd bootloaders output, press <enter> to get in fiq debugger and write "reboot" then <enter>.

=== Bootloaders outputs ===

first bootloader:

{{{

-----------------------------------------------------------

   Samsung Primitive Bootloader (PBL) v3.0

   Copyright (C) Samsung Electronics Co., Ltd. 2006-2010

-----------------------------------------------------------

Muxed OneNAND 512MB (0x50) Sync

Scanning Bad Block .......

Bad Block 77 (5)

Bad Block 295 (5)

Bad Block 1232 (5)

Bad Block 1646 (5)

Bad Block 1831 (5)

Bad Block 2047 (0)

SBL loadding success

Set cpu clk. from 400MHz to 800MHz.

OM=0x9, device=OnenandMux(Audi)

IROM e-fused - Secure Boot Version.

}}}

second bootloader:

{{{

-----------------------------------------------------------

   Samsung Secondary Bootloader (SBL) v3.0

   Copyright (C) Samsung Electronics Co., Ltd. 2006-2010

   Board Name: HERRING REV 52

   Build On: Jan 20 2011 17:19:41

-----------------------------------------------------------

MMC SEM16G 15188 MB

Re_partition: magic code(0x0)

Muxed OneNAND 512MB (0x50) Sync

Scanning Bad Block .......

Bad Block 77 (5)

Bad Block 295 (5)

Bad Block 1232 (5)

Bad Block 1646 (5)

Bad Block 1831 (5)

Bad Block 2047 (0)

Partitions loading success

Read image(PARAM) from flash .......

Done

init_fuel_gauge: vcell = 4083mV, soc = 94

PMIC_IRQ1    = 0xc0 

PMIC_IRQ2    = 0x0 

PMIC_IRQ3    = 0x0 

PMIC_IRQ4    = 0x0 

PMIC_STATUS1 = 0x0 

PMIC_STATUS2 = 0x0 

PMIC_STATUS3 = 0x0 

PMIC_STATUS4 = 0x0 

PMIC_STATUS5 = 0x0 

PMIC_SMPL    = 0x0 

Key scan = 0x0

message.command = 

message.status = 

message.recovery = 

}}}

second bootloader #2:

{{{

BOOT_MODE_NORMAL (SW_RST(0x00000004), INFORM(0x000000ee))

LCD ID = 0x0060a953

Done

Kernel(boot.img) read success from partition no.5

Setting param.serialnr = 0x3733bab6 0x6de200ec

Setting param.board_rev = 0x34

Setting param.cmdline = console=ttyFIQ0 no_console_suspend androidboot.serialno=3733BAB66DE200EC androidboot.bootloader=I9020XXKA3 androidboot.baseband=I9020XXKB3 androidboot.info=0x4,0xee,1 androidboot.carrier=EUR gain_code=3 s3cfb.bootloaderfb=0x34a00000 mach-herring.lcd_type=0x00000000 oem_state=unlocked 

Setting param.initrd_start = 0x31000000, param.initrd_size = 0x23265

Starting kernel at 0x30008000...

Uncompressing Linux... done, booting the kernel.

}}}

kernel

{{{

<hit enter to activate fiq debugger>

}}}

== TODO ==

 * Look if [http://www.glassechidna.com.au/products/heimdall/ Heimdall] can talk to the bootrom

 * Serial console:

  * Use the correct resistors enabling the serial console on the FSA9480

  * Mesure the voltage of the Nexus S serial port

  * Make a level shifter to shift the serial port levels 

  * Cross compile microcom or picocom 

  * get a serial console

 * Find the JTAG

 * look if the first stage bootloader(after the bootrom) is signed