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SciphoneDreamG2 » History » Version 13

marcin, 02/19/2016 10:49 PM

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= Sciphone Dream G2 =
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The Sciphone Dream G2 is a [wiki:MT6235] based phone running UI software to mimic the look+feel of Android.
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There is currently an u-boot and Linux port for the MT6235 underway, the primary development platform is the Sciphone G2.
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OsmocomBB does not yet support any Mediatek chipsets, so this phone is not supported by OsmocomBB.  Nonetheless, we
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expect to have support for it at some point in the future.
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More information on the hardware of the device can be found at [http://en.qi-hardware.com/wiki/Sciphone_Dream_G2]
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== Serial Cable ==
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You can make a serial cable by sacrificing the headset that comes with the phone, by swapping the pins inside the connector.
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Serial pinout:
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||Pin||signal||comment||
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||1||GND||
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||2||GND||
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||5||Rx||(From PC to Phone)||
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||7||Tx||(From Phone to PC)||
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[[Image(sciphone_serial.jpg,20%)]]
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== JTAG ==
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The JTAG port of the MT6235 is accessible on the phone PCB, see the attached picture.
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You can use [http://openocd.berlios.de/web/ OpenOCD] along with the attached configuration file ([raw-attachment:openocd_mt6235.cfg]) for debugging.
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[[Image(scig2_front.JPG,20%)]]
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[[Image(scig2_jtag.jpg,20%)]]
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== Serial Bootloader == 
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Like all Mediatek MT62xx !SoCs, the phone uses the [wiki:MTKRomloader].
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For executing U-Boot and Linux using the MTK romloader, proceed as follows:
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 * clone osmocom-bb.git and checkout the branch 'steve-m/loader_sciphone'
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 * compile the code, connect the phone and run osmocon:
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   {{{
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$ ./osmocon -p /dev/ttyUSB0 -m mtk ../../target/firmware/board/mt62xx/loader.mtkram.bin
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   }}}
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 * press and '''hold''' the powerbutton of the phone, until the loading has finished and you see the following:
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   {{{
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[...]
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Received branch address ack, code should run now
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Running on mt62xx in environment mtkram
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HW_CODE = 0x6235
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   }}}
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'''Uploading U-Boot'''
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 * '''don't''' terminate osmocon and execute:
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 {{{
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$ ./osmoload memload 0x500000 u-boot.bin
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$ ./osmoload jump 0x500000
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 }}}
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 * now terminate osmocon and open a serial terminal of your choice (115200-8N1)
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 * see below for loading Linux with U-Boot
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== MTK boot process ==
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MT62xx SoCs have IPL (Initial Program Loader) saved in ROM.[[BR]]
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This is first code executed after power up.[[BR]]
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It configures basic functionality of CPU (serial port 19200n8) and waits on 0xA beacon.[[BR]]
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If beacon won't be received, it jumps to NAND memory read procedure.[[BR]]
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At 0x0 address there is Boot Header placed which holds informations about NAND memory and parameters of image which is going to be loaded.[[BR]]
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NAND memory read procedure tries to read NAND memory from 0x0 address with following NFI controller settings:
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||Bus width||Address bytes||Page size||Column shift||Used in Sciphone G2||
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||1||3||512||8||||
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||0||3||512||8||||
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||1||4||512||8||||
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||0||4||512||8||yes||
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||1||4||2048||16||||
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||0||4||2048||16||yes||
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||1||5||2048||16||||
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||0||4||2048||16||||
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If Boot Header read from NAND memory will match to currently used NFI configuration, bootloader will start to read data from NAND to internal SRAM. Internal SRAM size is 64kB, which means that code loaded by IPL can't be bigger than that.[[BR]]
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'''Note:'''IPL doesn't configure PLL and SDRAM controller, so there is no possibility to load code to external RAM here.
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Here is were SPL (Secondary Program Loader) comes into the game.
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== SPL - Runing U-Boot from NAND ==
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SPL (Second Program Loader) is just small U-Boot loader which includes low level CPU initialization (PLL, SDRAM) and NAND driver.[[BR]]
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With default build it occupies less than 4kB, but it lacks NAND memory detection. All the NAND memory types can be specified using preprocessor which is not comfortable. We already identified three different NAND memories and that would be bad to create seperate builds for them.[[BR]]
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Fortunatelly there is no need to strip down SPL size to 4kB, so SPL code has been reworked and new functionalities are added. It detects NAND memory at startup and configures NFI controller automatically. New implementation can be found at "nand_spl/nand_boot_detect.c".[[BR]]
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SPL also automatically configures SDRAM controler according to RAM you have on your device (currently it tries two configurations).[[BR]]
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SPL is generated on every U-Boot build and binary can be found at "nand_spl/u-boot-spl.bin".[[BR]]
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SPL will be loaded and executed by IPL, only if Boot Header will contain valid data (in this case checksum and length is most important).[[BR]]
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There is already tool created which automatically generates Boot Header and places it at the begining of given binary. MTK Boot Header generator can be found at "tools/mtk_image.c".
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{{{
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Usage ./mtk_image [ -s size ] [ -o file ] mtk_dump.bin image.bin
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	[ -s size ]	- size of image, if not specified file size will be taken
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	[ -o file ]	- name of output file
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	mtk_dump.bin	- dump of NAND memory from address 0 (at least 64 bytes)
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	image.bin	- image to be loaded by MTK bootloader
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}}}
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== U-Boot ==
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Port of U-Boot for Sciphone G2 can be found at [http://git.osmocom.org/gitweb?p=uboot-mt623x.git;a=summary U-Boot]
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Building U-Boot:
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{{{
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export CROSS_COMPILE=arm-linux-gnueabi-
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make sciphone_g2_config
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make
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}}}
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== Linux kernel ==
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Port of Linux kernel for Sciphone G2 can be found at [http://git.osmocom.org/gitweb?p=linux-mt623x.git;a=summary Linux kernel]
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Building Linux:
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{{{
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export CROSS_COMPILE=arm-linux-gnueabi-
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make ARCH=arm sciphone_g2_defconfig
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make ARCH=arm uImage
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}}}
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== Building initramfs file system ==
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The easiest way to have file system in Linux kernel is to build [http://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt Initramfs image].[[BR]]
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You need to download [http://www.busybox.net/ Busybox], configure it and build it.
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{{{
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export CROSS_COMPILE=arm-linux-gnueabi-
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make menuconfig
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make
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make install
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}}}
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Generated file system by default installs in _install directory.[[BR]]
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Additional to that you'll need to create console device in already built filesystem.
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{{{
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sudo mknod dev/console c 5 1
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}}}
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Now you can create CPIO archive:
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{{{
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find . | cpio -o -H newc > rootfs.cpio
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}}}
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Next step is to point to Linux kernel where initramfs image is located.[[BR]]
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In menuconfig of Linux kernel you should modify following option:
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{{{
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CONFIG_INITRAMFS_SOURCE=<path_to_cpio>
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General setup -> Initial RAM filesystem and RAM disk -> Initramfs source file(s)
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}}}
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After these steps Linux kernel image will have initramfs built in.[[BR]]
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'''Important note:''' Initramfs ignores 'init=' variable given in kernel boot parameters list. It always executes /init command at startup and you can't change it. Check if you have /init in your file system (BusyBox has /linuxrc by default, so just change its name to init).
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Every time you change initramfs file system you have to rebuild also Linux kernel.[[BR]]
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To unpack CPIO archive you can use following command:
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{{{
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cpio -i -d -H newc -F <path_to_cpio_archive> --no-absolute-filenames
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}}}
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== Reading data files in U-Boot ==
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'''NAND'''
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Following command will read 256 bytes from NAND address 0 at address 0x800000.
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{{{
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nand read 0x800000 0 0x100
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}}}
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'''Serial'''
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Following command will read data at address 0x800000 from serial at baudrate 115200 (using kermit protocol).
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{{{
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loadb 0x800000 115200
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}}}
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'''SD/MMC'''
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Following command will read uImage file at address 0x800000 from MMC card.
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{{{
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fatload mmc 0 0x800000 uImage
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}}}
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== NAND memory ==
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So far three types of NAND memories has been identified:
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||Chip||Size||
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||HY27XS08121M||512Mb (64MB) NAND||
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||HY27XA081G1M||1Gb (128MB) NAND||
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||TC58NVG0S3AFT||1Gb (128MB) NAND||
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All of them are supported by "mt62xx_nand.c" NAND driver in U-Boot.[[BR]]
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This driver has also support for ECC hardware decoding and encoding.[[BR]]
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ECC layout which is used by MTK looks as follows:
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{{{
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/*
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 * For small and large page NAND devices ecc block size is the same:
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 *
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 *      ecc_block_size = 256
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 *
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 * Placement of ecc bytes in spare area is as follows:
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 *
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 * --------------------------------------------------------------
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 * |                            SPARE                           |
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 * --------------------------------------------------------------
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 * |    | ECC0  |       | ECC1  |       | ECC2  |       | ECC3  |
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 * --------------------------------------------------------------
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 * 0    8       16      24      32      40      48      56      64
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 *
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 * ECC0 = 12 bits (from 1st ECC block) + 12 bits (from 2nd ECC block)
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 * ECC1 = 12 bits (from 3rd ECC block) + 12 bits (from 4th ECC block)
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 * ECC2 = 12 bits (from 5th ECC block) + 12 bits (from 6th ECC block)
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 * ECC2 = 12 bits (from 7th ECC block) + 12 bits (from 8th ECC block)
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 */
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}}}
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ECC layout information is pretty important as built-in bootloader in MT62xx chips
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has hardware ECC enabled and it won't load code from NAND if ECC layout will
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not match.[[BR]]
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This layout is also important to properly dump or restore existing firmware.[[BR]]
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NAND driver for Linux is under development.
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== LCD ==
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Sciphone G2 has LCD with 240x320 resolution.[[BR]]
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Currently two different LCD controllers has been identified (on Sciphone G2):
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 * ILI9331
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 * ILI9325
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These controllers are already supported in U-Boot.[[BR]]
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To identify what kind of controller is in your device, just check U-Boot prints.
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{{{
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DRAM:  32 MiB
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NAND:  64 MiB
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MMC:   msdc_mmc: 0
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mtk_lcd INFO: Read LCD device code: 9331.
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}}}
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U-Boot supports displaying bitmap on the screen, you just have to create bitmap in proper format.[[BR]]
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By default U-Boot will build osmocomBB bitmap.[[BR]]
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To convert your customized bitmap change type of bitmap to indexed.[[BR]]
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Using GIMP, select "Image -> Mode -> Indexed...". Maximum number of colours is 240 (16 is used by internal U-Boot CMAP).[[BR]]
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In existing U-Boot bmp logo converting tool (tools/bmp_logo.c) there are two issues:
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 * width of bitmap has to be aligned to 4 (otherwise padding bytes will be added and bitmap will be not properly displayed)
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 * size of bitmap can't be bigger than 65535 (LCD on Sciphone G2 is 240x320 = 76800)
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Both issues are fixed on [http://git.osmocom.org/gitweb?p=uboot-mt623x.git;a=summary uboot-mt623x].[[BR]]
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MT6235 LCD controller shares data lines with NFI (NAND) controller. Currently there is no possibility to use NAND when LCD is used.[[BR]]
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Frame buffer driver for Linux is under development.
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== U-Boot BBT handling ==
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Comment from "sciphone_g2.h" configuration file explains how BBT is handled.
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{{{
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/*
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 * Below option allows U-Boot to save BBT table in NAND.
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 * Without this option BBT table is created everytime when first nand
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 * command is executed (except "nand dump"). Full scanning of NAND
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 * takes long time and unnecessarily delays first command execution.
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 *
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 * NOTE! This option is disabled by defaut as at startup it deletes last
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 * two blocks of NAND. Most of people run code from RAM and don't have
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 * NAND memory dumped yet. If you don't like to wait on first nand
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 * command, you should enable below option.
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 */
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#define MT62XX_NAND_BBT_IN_NAND
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}}}
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== MTD partitions ==
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Layout of MTD partitions is following:
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{{{
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device nand0 <mt62xx_nand.0>, # parts = 5
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 #: name                size            offset          mask_flags
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 0: sbl                 0x00020000      0x00000000      0
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 1: env                 0x00020000      0x00020000      0
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 2: u-boot              0x00200000      0x00040000      0
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 3: kernel              0x00200000      0x00240000      0
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 4: root                0x03bc0000      0x00440000      0
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}}}
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