+ 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;