- NOTE: for embedded systems where boot time is critical you can trade
- speed for memory and install an UNCOMPRESSED image instead: this
- needs more space in Flash, but boots much faster since it does not
- need to be uncompressed:
-
- -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz
- -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
- > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
- > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux \
- > examples/uImage.TQM850L-uncompressed
- Image Name: 2.4.4 kernel for TQM850L
- Created: Wed Jul 19 02:34:59 2000
- Image Type: PowerPC Linux Kernel Image (uncompressed)
- Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
- Load Address: 0x00000000
- Entry Point: 0x00000000
-
-
- Similar you can build U-Boot images from a 'ramdisk.image.gz' file
- when your kernel is intended to use an initial ramdisk:
-
- -> tools/mkimage -n 'Simple Ramdisk Image' \
- > -A ppc -O linux -T ramdisk -C gzip \
- > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
- Image Name: Simple Ramdisk Image
- Created: Wed Jan 12 14:01:50 2000
- Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
- Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
- Load Address: 0x00000000
- Entry Point: 0x00000000
-
-
- Installing a Linux Image:
- -------------------------
-
- To downloading a U-Boot image over the serial (console) interface,
- you must convert the image to S-Record format:
-
- objcopy -I binary -O srec examples/image examples/image.srec
-
- The 'objcopy' does not understand the information in the U-Boot
- image header, so the resulting S-Record file will be relative to
- address 0x00000000. To load it to a given address, you need to
- specify the target address as 'offset' parameter with the 'loads'
- command.
-
- Example: install the image to address 0x40100000 (which on the
- TQM8xxL is in the first Flash bank):
-
- => erase 40100000 401FFFFF
-
- .......... done
- Erased 8 sectors
-
- => loads 40100000
- ## Ready for S-Record download ...
- ~>examples/image.srec
- 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
- ...
- 15989 15990 15991 15992
- [file transfer complete]
- [connected]
- ## Start Addr = 0x00000000
-
-
- You can check the success of the download using the 'iminfo' command;
- this includes a checksum verification so you can be sure no data
- corruption happened:
-
- => imi 40100000
-
- ## Checking Image at 40100000 ...
- Image Name: 2.2.13 for initrd on TQM850L
- Image Type: PowerPC Linux Kernel Image (gzip compressed)
- Data Size: 335725 Bytes = 327 kB = 0 MB
- Load Address: 00000000
- Entry Point: 0000000c
- Verifying Checksum ... OK
-
-
- Boot Linux:
- -----------
-
- The "bootm" command is used to boot an application that is stored in
- memory (RAM or Flash). In case of a Linux kernel image, the contents
- of the "bootargs" environment variable is passed to the kernel as
- parameters. You can check and modify this variable using the
- "printenv" and "setenv" commands:
-
-
- => printenv bootargs
- bootargs=root=/dev/ram
-
- => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
-
- => printenv bootargs
- bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
-
- => bootm 40020000
- ## Booting Linux kernel at 40020000 ...
- Image Name: 2.2.13 for NFS on TQM850L
- Image Type: PowerPC Linux Kernel Image (gzip compressed)
- Data Size: 381681 Bytes = 372 kB = 0 MB
- Load Address: 00000000
- Entry Point: 0000000c
- Verifying Checksum ... OK
- Uncompressing Kernel Image ... OK
- Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
- Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
- time_init: decrementer frequency = 187500000/60
- Calibrating delay loop... 49.77 BogoMIPS
- Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
- ...
-
- If you want to boot a Linux kernel with initial ram disk, you pass
- the memory addresses of both the kernel and the initrd image (PPBCOOT
- format!) to the "bootm" command:
-
- => imi 40100000 40200000
-
- ## Checking Image at 40100000 ...
- Image Name: 2.2.13 for initrd on TQM850L
- Image Type: PowerPC Linux Kernel Image (gzip compressed)
- Data Size: 335725 Bytes = 327 kB = 0 MB
- Load Address: 00000000
- Entry Point: 0000000c
- Verifying Checksum ... OK
-
- ## Checking Image at 40200000 ...
- Image Name: Simple Ramdisk Image
- Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
- Data Size: 566530 Bytes = 553 kB = 0 MB
- Load Address: 00000000
- Entry Point: 00000000
- Verifying Checksum ... OK
-
- => bootm 40100000 40200000
- ## Booting Linux kernel at 40100000 ...
- Image Name: 2.2.13 for initrd on TQM850L
- Image Type: PowerPC Linux Kernel Image (gzip compressed)
- Data Size: 335725 Bytes = 327 kB = 0 MB
- Load Address: 00000000
- Entry Point: 0000000c
- Verifying Checksum ... OK
- Uncompressing Kernel Image ... OK
- ## Loading RAMDisk Image at 40200000 ...
- Image Name: Simple Ramdisk Image
- Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
- Data Size: 566530 Bytes = 553 kB = 0 MB
- Load Address: 00000000
- Entry Point: 00000000
- Verifying Checksum ... OK
- Loading Ramdisk ... OK
- Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
- Boot arguments: root=/dev/ram
- time_init: decrementer frequency = 187500000/60
- Calibrating delay loop... 49.77 BogoMIPS
- ...
- RAMDISK: Compressed image found at block 0
- VFS: Mounted root (ext2 filesystem).
-
- bash#
-
- More About U-Boot Image Types:
- ------------------------------
-
- U-Boot supports the following image types:
-
- "Standalone Programs" are directly runnable in the environment
- provided by U-Boot; it is expected that (if they behave
- well) you can continue to work in U-Boot after return from
- the Standalone Program.
- "OS Kernel Images" are usually images of some Embedded OS which
- will take over control completely. Usually these programs
- will install their own set of exception handlers, device
- drivers, set up the MMU, etc. - this means, that you cannot
- expect to re-enter U-Boot except by resetting the CPU.
- "RAMDisk Images" are more or less just data blocks, and their
- parameters (address, size) are passed to an OS kernel that is
- being started.
- "Multi-File Images" contain several images, typically an OS
- (Linux) kernel image and one or more data images like
- RAMDisks. This construct is useful for instance when you want
- to boot over the network using BOOTP etc., where the boot
- server provides just a single image file, but you want to get
- for instance an OS kernel and a RAMDisk image.
-
- "Multi-File Images" start with a list of image sizes, each
- image size (in bytes) specified by an "uint32_t" in network
- byte order. This list is terminated by an "(uint32_t)0".
- Immediately after the terminating 0 follow the images, one by
- one, all aligned on "uint32_t" boundaries (size rounded up to
- a multiple of 4 bytes).
-
- "Firmware Images" are binary images containing firmware (like
- U-Boot or FPGA images) which usually will be programmed to
- flash memory.
-
- "Script files" are command sequences that will be executed by
- U-Boot's command interpreter; this feature is especially
- useful when you configure U-Boot to use a real shell (hush)
- as command interpreter.
-
-
- Standalone HOWTO:
- =================
-
- One of the features of U-Boot is that you can dynamically load and
- run "standalone" applications, which can use some resources of
- U-Boot like console I/O functions or interrupt services.
-
- Two simple examples are included with the sources:
-
- "Hello World" Demo:
- -------------------
-
- 'examples/hello_world.c' contains a small "Hello World" Demo
- application; it is automatically compiled when you build U-Boot.
- It's configured to run at address 0x00040004, so you can play with it
- like that:
-
- => loads
- ## Ready for S-Record download ...
- ~>examples/hello_world.srec
- 1 2 3 4 5 6 7 8 9 10 11 ...
- [file transfer complete]
- [connected]
- ## Start Addr = 0x00040004
-
- => go 40004 Hello World! This is a test.
- ## Starting application at 0x00040004 ...
- Hello World
- argc = 7
- argv[0] = "40004"
- argv[1] = "Hello"
- argv[2] = "World!"
- argv[3] = "This"
- argv[4] = "is"
- argv[5] = "a"
- argv[6] = "test."
- argv[7] = "<NULL>"
- Hit any key to exit ...
-
- ## Application terminated, rc = 0x0
-
- Another example, which demonstrates how to register a CPM interrupt
- handler with the U-Boot code, can be found in 'examples/timer.c'.
- Here, a CPM timer is set up to generate an interrupt every second.
- The interrupt service routine is trivial, just printing a '.'
- character, but this is just a demo program. The application can be
- controlled by the following keys:
-
- ? - print current values og the CPM Timer registers
- b - enable interrupts and start timer
- e - stop timer and disable interrupts
- q - quit application
-
- => loads
- ## Ready for S-Record download ...
- ~>examples/timer.srec
- 1 2 3 4 5 6 7 8 9 10 11 ...
- [file transfer complete]
- [connected]
- ## Start Addr = 0x00040004
-
- => go 40004
- ## Starting application at 0x00040004 ...
- TIMERS=0xfff00980
- Using timer 1
- tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
-
- Hit 'b':
- [q, b, e, ?] Set interval 1000000 us
- Enabling timer
- Hit '?':
- [q, b, e, ?] ........
- tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
- Hit '?':
- [q, b, e, ?] .
- tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
- Hit '?':
- [q, b, e, ?] .
- tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
- Hit '?':
- [q, b, e, ?] .
- tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
- Hit 'e':
- [q, b, e, ?] ...Stopping timer
- Hit 'q':
- [q, b, e, ?] ## Application terminated, rc = 0x0
-
-
- Minicom warning:
- ================
-
- Over time, many people have reported problems when trying to use the
- "minicom" terminal emulation program for serial download. I (wd)
- consider minicom to be broken, and recommend not to use it. Under
- Unix, I recommend to use C-Kermit for general purpose use (and
- especially for kermit binary protocol download ("loadb" command), and
- use "cu" for S-Record download ("loads" command).
-
- Nevertheless, if you absolutely want to use it try adding this
- configuration to your "File transfer protocols" section:
-
- Name Program Name U/D FullScr IO-Red. Multi
- X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
- Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
-
-
- NetBSD Notes:
- =============
-
- Starting at version 0.9.2, U-Boot supports NetBSD both as host
- (build U-Boot) and target system (boots NetBSD/mpc8xx).
-
- Building requires a cross environment; it is known to work on
- NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
- need gmake since the Makefiles are not compatible with BSD make).
- Note that the cross-powerpc package does not install include files;
- attempting to build U-Boot will fail because <machine/ansi.h> is
- missing. This file has to be installed and patched manually:
-
- # cd /usr/pkg/cross/powerpc-netbsd/include
- # mkdir powerpc
- # ln -s powerpc machine
- # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
- # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
-
- Native builds *don't* work due to incompatibilities between native
- and U-Boot include files.
-
- Booting assumes that (the first part of) the image booted is a
- stage-2 loader which in turn loads and then invokes the kernel
- proper. Loader sources will eventually appear in the NetBSD source
- tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
- meantime, send mail to bruno@exet-ag.de and/or wd@denx.de for
- details.
-
-
- Implementation Internals:
- =========================
-
- The following is not intended to be a complete description of every
- implementation detail. However, it should help to understand the
- inner workings of U-Boot and make it easier to port it to custom
- hardware.
-
-
- Initial Stack, Global Data:
- ---------------------------
-
- The implementation of U-Boot is complicated by the fact that U-Boot
- starts running out of ROM (flash memory), usually without access to
- system RAM (because the memory controller is not initialized yet).
- This means that we don't have writable Data or BSS segments, and BSS
- is not initialized as zero. To be able to get a C environment working
- at all, we have to allocate at least a minimal stack. Implementation
- options for this are defined and restricted by the CPU used: Some CPU
- models provide on-chip memory (like the IMMR area on MPC8xx and
- MPC826x processors), on others (parts of) the data cache can be
- locked as (mis-) used as memory, etc.
-
- Chris Hallinan posted a good summary of these issues to the
- u-boot-users mailing list:
-
- Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
- From: "Chris Hallinan" <clh@net1plus.com>
- Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
- ...
-
- Correct me if I'm wrong, folks, but the way I understand it
- is this: Using DCACHE as initial RAM for Stack, etc, does not
- require any physical RAM backing up the cache. The cleverness
- is that the cache is being used as a temporary supply of
- necessary storage before the SDRAM controller is setup. It's
- beyond the scope of this list to expain the details, but you
- can see how this works by studying the cache architecture and
- operation in the architecture and processor-specific manuals.
-
- OCM is On Chip Memory, which I believe the 405GP has 4K. It
- is another option for the system designer to use as an
- initial stack/ram area prior to SDRAM being available. Either
- option should work for you. Using CS 4 should be fine if your
- board designers haven't used it for something that would
- cause you grief during the initial boot! It is frequently not
- used.
-
- CFG_INIT_RAM_ADDR should be somewhere that won't interfere
- with your processor/board/system design. The default value
- you will find in any recent u-boot distribution in
- Walnut405.h should work for you. I'd set it to a value larger
- than your SDRAM module. If you have a 64MB SDRAM module, set
- it above 400_0000. Just make sure your board has no resources
- that are supposed to respond to that address! That code in
- start.S has been around a while and should work as is when
- you get the config right.
-
- -Chris Hallinan
- DS4.COM, Inc.
-
- It is essential to remember this, since it has some impact on the C
- code for the initialization procedures:
-
- * Initialized global data (data segment) is read-only. Do not attempt
- to write it.
-
- * Do not use any unitialized global data (or implicitely initialized
- as zero data - BSS segment) at all - this is undefined, initiali-
- zation is performed later (when relocating to RAM).
-
- * Stack space is very limited. Avoid big data buffers or things like
- that.
-
- Having only the stack as writable memory limits means we cannot use
- normal global data to share information beween the code. But it
- turned out that the implementation of U-Boot can be greatly
- simplified by making a global data structure (gd_t) available to all
- functions. We could pass a pointer to this data as argument to _all_
- functions, but this would bloat the code. Instead we use a feature of
- the GCC compiler (Global Register Variables) to share the data: we
- place a pointer (gd) to the global data into a register which we
- reserve for this purpose.
-
- When choosing a register for such a purpose we are restricted by the
- relevant (E)ABI specifications for the current architecture, and by
- GCC's implementation.
-
- For PowerPC, the following registers have specific use:
- R1: stack pointer
- R2: TOC pointer
- R3-R4: parameter passing and return values
- R5-R10: parameter passing
- R13: small data area pointer
- R30: GOT pointer
- R31: frame pointer
-
- (U-Boot also uses R14 as internal GOT pointer.)
-
- ==> U-Boot will use R29 to hold a pointer to the global data
-
- Note: on PPC, we could use a static initializer (since the
- address of the global data structure is known at compile time),
- but it turned out that reserving a register results in somewhat
- smaller code - although the code savings are not that big (on
- average for all boards 752 bytes for the whole U-Boot image,
- 624 text + 127 data).
-
- On ARM, the following registers are used:
-
- R0: function argument word/integer result
- R1-R3: function argument word
- R9: GOT pointer
- R10: stack limit (used only if stack checking if enabled)
- R11: argument (frame) pointer
- R12: temporary workspace
- R13: stack pointer
- R14: link register
- R15: program counter
-
- ==> U-Boot will use R8 to hold a pointer to the global data
-
-
- Memory Management:
- ------------------
-
- U-Boot runs in system state and uses physical addresses, i.e. the
- MMU is not used either for address mapping nor for memory protection.
-
- The available memory is mapped to fixed addresses using the memory
- controller. In this process, a contiguous block is formed for each
- memory type (Flash, SDRAM, SRAM), even when it consists of several
- physical memory banks.
-
- U-Boot is installed in the first 128 kB of the first Flash bank (on
- TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
- booting and sizing and initializing DRAM, the code relocates itself
- to the upper end of DRAM. Immediately below the U-Boot code some
- memory is reserved for use by malloc() [see CFG_MALLOC_LEN
- configuration setting]. Below that, a structure with global Board
- Info data is placed, followed by the stack (growing downward).
-
- Additionally, some exception handler code is copied to the low 8 kB
- of DRAM (0x00000000 ... 0x00001FFF).
-
- So a typical memory configuration with 16 MB of DRAM could look like
- this:
-
- 0x0000 0000 Exception Vector code
- :
- 0x0000 1FFF
- 0x0000 2000 Free for Application Use
- :
- :
-
- :
- :
- 0x00FB FF20 Monitor Stack (Growing downward)
- 0x00FB FFAC Board Info Data and permanent copy of global data
- 0x00FC 0000 Malloc Arena
- :
- 0x00FD FFFF
- 0x00FE 0000 RAM Copy of Monitor Code
- ... eventually: LCD or video framebuffer
- ... eventually: pRAM (Protected RAM - unchanged by reset)
- 0x00FF FFFF [End of RAM]
-
-
- System Initialization:
- ----------------------
-
- In the reset configuration, U-Boot starts at the reset entry point
- (on most PowerPC systens at address 0x00000100). Because of the reset
- configuration for CS0# this is a mirror of the onboard Flash memory.
- To be able to re-map memory U-Boot then jumps to its link address.
- To be able to implement the initialization code in C, a (small!)
- initial stack is set up in the internal Dual Ported RAM (in case CPUs
- which provide such a feature like MPC8xx or MPC8260), or in a locked
- part of the data cache. After that, U-Boot initializes the CPU core,
- the caches and the SIU.
-
- Next, all (potentially) available memory banks are mapped using a
- preliminary mapping. For example, we put them on 512 MB boundaries
- (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
- on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
- programmed for SDRAM access. Using the temporary configuration, a
- simple memory test is run that determines the size of the SDRAM
- banks.
-
- When there is more than one SDRAM bank, and the banks are of
- different size, the largest is mapped first. For equal size, the first
- bank (CS2#) is mapped first. The first mapping is always for address
- 0x00000000, with any additional banks following immediately to create
- contiguous memory starting from 0.
-
- Then, the monitor installs itself at the upper end of the SDRAM area
- and allocates memory for use by malloc() and for the global Board
- Info data; also, the exception vector code is copied to the low RAM
- pages, and the final stack is set up.
-
- Only after this relocation will you have a "normal" C environment;
- until that you are restricted in several ways, mostly because you are
- running from ROM, and because the code will have to be relocated to a
- new address in RAM.
-
-
- U-Boot Porting Guide:
- ----------------------
-
- [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
- list, October 2002]
-
-
- int main (int argc, char *argv[])
- {
- sighandler_t no_more_time;
-
- signal (SIGALRM, no_more_time);
- alarm (PROJECT_DEADLINE - toSec (3 * WEEK));
-
- if (available_money > available_manpower) {
- pay consultant to port U-Boot;
- return 0;
- }
-
- Download latest U-Boot source;
-
- Subscribe to u-boot-users mailing list;
-
- if (clueless) {
- email ("Hi, I am new to U-Boot, how do I get started?");
- }
-
- while (learning) {
- Read the README file in the top level directory;
- Read http://www.denx.de/twiki/bin/view/DULG/Manual ;
- Read the source, Luke;
- }
-
- if (available_money > toLocalCurrency ($2500)) {
- Buy a BDI2000;
- } else {
- Add a lot of aggravation and time;
- }
-
- Create your own board support subdirectory;
-
- Create your own board config file;
-
- while (!running) {
- do {
- Add / modify source code;
- } until (compiles);
- Debug;
- if (clueless)
- email ("Hi, I am having problems...");
- }
- Send patch file to Wolfgang;
projects / u-boot / blobdiff