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-
- U-Boot for Nios-32
-
- Last Update: February 1, 2004
-====================================================================
-
-This file contains information regarding U-Boot and the Altera
-Nios CPU. For information regarding U-Boot and the Nios Development
-Kits see:
-
- * Cyclone Edition (DK-1C20), see doc/README.dk1c20
- * Stratix Edition (DK-1S10), see doc/README.dk1s10 (TODO)
- * Stratix Edition (DK-1S40), see doc/README.dk1s40 (TODO)
- * Stratix Edition (DK-20K200), see doc/README.dk20k200 (TODO)
-
-For informations regarding Nios Development Kit hardware overview
-and the NIOS CPU standard configuration of all known boards made by
-Altera see:
-
- * Development Kit (DK) hardware overview, see doc/README.nios_DK
- * NIOS CPU standard_32 at DK-1C20, see doc/README.dk1c20_std32
- * NIOS CPU standard_32 at DK-1S10, see doc/README.dk1s10_std32
- * NIOS CPU standard_32 at DK-1S40, see doc/README.dk1s40_std32
- * NIOS CPU standard_32 at DK-20K200, see doc/README.dk20k200_std32
-
-For those interested in contributing ... see HELP WANTED below.
-
-
-1. OVERVIEW
-------------
-
-U-Boot has been successfully tested on the Nios Cyclone development
-board using both the 'safe' and 'standard 32' configurations with
-Nios CPU revision 3.1 (CPU_ID = 0x3018). U-Boot can be used with
-or without the GERMS monitor. The initial version of U-Boot for the
-Cyclone development kit is about 60 Kbyte and will fit in a single
-sector of on-board FLASH. Only the Nios 32-bit CPU is supported.
-
-1.1 GERMS Monitor
-------------------
-If GERMS is just not enough, then U-Boot is a great antibiotic.
-You will be very pleased with its high degree of configurability
-and its rich feature set.
-
-A few of the most obvious limitations of GERMS are overcome by
-using U-Boot (See 'Brain Damage'). Most notably, you can use
-minicom or Hyperterminal (duh).
-
-1.2 Altera Source Code
------------------------
-The Nios port does NOT include ANY sources that Altera has the
-copyright. This was a conscious decision ... not an accident.
-The Altera license is not clear in terms of distributing Altera
-sources (when altera silicon is not involved). This isn't really
-a problem as little, if any, of the Altera source contains
-features that are not already available in U-Boot.
-
-1.3 Debugging via OCI
----------------------
-The Nios port supports debugging with gdb and/or nios-console
-via the JTAG port. Stubs for debugging with gdb via the serial
-port are not currently implemented.
-
-
-2. CONFIGURATION OPTIONS/SETTINGS
-----------------------------------
-
-2.1 Nios-specific Options/Settings
------------------------------------
-All configuration options/settings that are specific to Nios begin
-with "CONFIG_NIOS_", "CONFIG_SYS_NIOS_", or "CONFIG_SYS_NIOS_CPU_".
-
-The configuration follows a two-stage process. In the first stage
-the NIOS CPU core will defined like defined in Alteras SOPC Builder.
-At this point we use the "CONFIG_SYS_NIOS_CPU_" defines exclusively. For
-more informations about all the definitions you have to setup see
-into current board configurations and doc/README.nios_CFG_NIOS_CPU.
-
-In second stage we bring the NIOS CPU configuration in relation to
-U-Boot configuration options/settings. The following is a list of
-currently defined Nios-specific options/parameters used inside of
-U-Boot. If any options are related to Standard-32 Nios SDK
-excalibur.h definitions, the related definition follows the
-description).
-
-CONFIG_NIOS -- defined for all Nios-32 boards.
-
-CONFIG_SYS_NIOS_CONSOLE -- the base address of the console UART or the JTAG
- stdio port. To enable a console via JTAG, define
- CONFIG_CONSOLE_JTAG and set CGF_NIOS_CONSOLE to the base address
- of the JTAG stdio port (normally OCI base + 0x00fa). Then
- run nios-console with the -w option.
- (standard-32: nasys_uart_0 resp. na_uart1_base).
-
-CONFIG_SYS_NIOS_FIXEDBAUD -- defined if the console UART PTF fixed_baud
- parameter is set to '1'.
-
-CONFIG_SYS_NIOS_MULT_HW -- use full hardware multiply (not yet implemented).
-
-CONFIG_SYS_NIOS_MULT_MSTEP -- use hardware assisted multiply using the
- MSTEP instruction (not yet implemented).
-
-CONFIG_SYS_NIOS_TMRBASE -- the base address of the timer used to support
- xxx_timer routines (e.g. set_timer(), get_timer(), etc.).
- (standard-32: nasys_timer_1 resp. na_lo_priority_timer2_base).
-
-CONFIG_SYS_NIOS_TMRIRQ -- the interrupt request (vector number) assigned to
- the timer. (standard-32: nasys_timer_1_irq resp.
- na_low_priority_timer2_irq).
-
-CONFIG_SYS_NIOS_TMRMS -- the period of the timer in milliseconds.
-
-CONFIG_SYS_NIOS_TMRCNT -- the preloadable counter value for the timer if it has
- no fixed period.
-
-CONFIG_SYS_NIOS_ASMIBASE -- the base address of the ASMI peripheral.
- (standard-32: na_asmi_base).
-
-CONFIG_SYS_NIOS_SPIBASE -- the base address of the SPI master (!) peripheral.
- (nasys_spi_0)
-
-CONFIG_SYS_NIOS_SPIBITS -- the amount of configured SPI data bits in PTF.
- This value can be 8 or 16 only! (PTF: databits)
-
-
-2.2 Differences in U-Boot Options/Settings
--------------------------------------------
-Some 'standard' U-Boot options/settings are treated differently in
-the Nios port. These are described below.
-
-CONFIG_SYS_GBL_DATA_OFFSET -- in the Nios port, this is the offset of the
- global data structure in the Nios memory space. More simply,
- the address of global data.
-
-
-3. ASSEMBLY CODING
--------------------
-
-In browsing the assembly source files, you may notice the absence
-of the 'magic macros' (e.g. MOVIA, MOVIP, ADDIP etc.). This is
-deliberate. The documentation for the magic macros is scant and
-it is hard to find ... it does not appear in the Nios programmer's
-manual, nor does it appear in the assembler manual. Regardless,
-the macros actually do very little to improve readability anyway.
-
-With this in mind, all assembler modules use only instructions that
-appear in the Nios programmer's manual OR are directly supported
-by the nios-elf toolchain. For example, the 'dec %rB' instruction
-is an alias for 'subi %rB,1' that is supported by the assembler
-but does not appear in the programmer's manual.
-
-
-4. BOOT PROCESS
----------------
-
-4.1 Boot process over GERMS
----------------------------
-When the NIOS CPU catch a reset signal it will begin to be running
-code from CONFIG_SYS_NIOS_CPU_RST_VECT. Normally at this place it will
-find the GERMS monitor. That's the case for the generic NIOS CPU
-configuration "standard_32". When the GERMS monitor starts running,
-it performs important system initializations and then looks for
-executable code in flash, using the following steps:
-
- 1. Examining the two bytes at CONFIG_SYS_NIOS_CPU_FLASH_BASE + 0x04000C.
- 2. Examining the button 0 on the PIO CONFIG_SYS_NIOS_CPU_BUTTON_PIO.
- 3. If the button is not pressed and the two bytes contain 'N'
- and 'i', the monitor executes a CALL to location
- CONFIG_SYS_NIOS_CPU_FLASH_BASE + 0x040000.
- 4. If the code is not executed in step 3 or the code returns,
- then prints an 8-digit version number to STDOUT and waits for
- user commands from STDIN.
-
-In normal case, for "standard_32", STDIN and STDOUT are the first
-serial port.
-
-4.2 Return to GERMS command line
---------------------------------
-During the boot process, the GERMS monitor checks for the existence
-of application software in flash memory. If found, the processor
-immediately executes the code. To return program execution to the
-GERMS monitor (that is, avoid running code stored in flash memory):
-
- 1. Hold down CONFIG_SYS_NIOS_CPU_BUTTON_PIO, button number 0.
- 2. Press then release the CPU reset button.
- 3. Release CONFIG_SYS_NIOS_CPU_BUTTON_PIO, button number 0.
-
-
-5. DEBUGGING WITH GDB
----------------------
-
-Debug sessions using gdb are currently supported only via JTAG. The
-stubs for debugging via a serial port are not implemented. To enable
-the gdb JTAG stubs, simply reference _brkpt_hw_int and _brkpt_sw_int
-at vector table offsets 3 and 4, respectively. For an example, see
-board/altera/dk1c20/vectors.S.
-
-5.1 Vector Table Initialization and ROM Stubs
----------------------------------------------
-If CONFIG_ROM_STUBS is defined, the debug breakpoint and single step
-entries in the vector table are restored to their initial values
-immediately _after_ initializing the vector table. Defining this macro
-is useful when ROM-based stubs are implemented.
-
-NOTE: The default GERMS monitor does NOT implement gdb stubs, nor does
-it initialize the vector table. Therefore, when debugging U-Boot, you
-should NOT set a software breakpoint prior to vector table initialization.
-
-5.2 Starting a Debug Session
-----------------------------
-If you're not familiar with gdb, you follow these step-by-step instructions.
-These instructions are NOT the only way to start a debug session, but they
-cover most of the individual functions to get you started.
-
- 1. Start the JTAG gdb server. Open a Nios shell window and start
- the server. When the server is started you must provide the base
- address of the OCI core. For example, when using the Cyclone
- development kit (DK1C20):
-
- $ nios-gdb-server --ocibase=0x00920800 --tcpport=2342
-
- 2. Start gdb. Open a Nios shell window, change to the top-level
- U-Boot directory and start gdb, specifying the u-boot elf file:
-
- $ nios-elf-gdb u-boot
-
- 3. Update target settings. From the file menu, select
- "Target Settings ..." and select the following, then click 'Ok':
-
- Target: Remote/TCP
- Port : 2342 (same as in step 1)
- Display download dialog: checked
- All other check boxes: unchecked
-
- 4. Connect to the target. Select menu: 'Run->Connect to target'.
- You should see a dialog box indicating the you successfully connected
- to the target.
-
- 5. Download U-Boot. Select menu: 'Run->Download'.
-
- 6. Open a gdb console window and set the source directory paths.
- Select menu: 'View->Console'. In the console window, enter the
- following commands, then close the console window:
-
- (gdb) directory common
- (gdb) directory arch/nios/cpu
- (gdb) directory arch/nios/lib
- (gdb) directory board/altera/dk1c20
-
- Note that the last command is for the DK1C20 board only. If you
- are using another board, specify that board's directory.
-
- 7. Open the file board.c (using the file menu in the lower
- left hand corner). Scroll to the board_init() routine and set
- a breakpoint.
-
- 8. Run U-Boot. Just click on the run icon, or select menu:
- 'Run->Run'. U-Boot should start running, then break at your
- breakpoint.
-
- 9. Have fun & start learning more about gdb.
-
-
-5.3 For advanced Users
-----------------------
-A few notes for those more familiar with gdb.
-
- -Serial port stubs are not implemented. Sorry, but it's just not
- worth _my_ effort. The JTAG stubs work great and are ridiculously
- simple to implement.
-
- -If you need to debug the early startup code (prior to the vector
- table initialization), use the nios-console debugger.
-
- - Connect, download & run -- there are some problems here. Connect
- download and run seperately to avoid trouble.
-
-6. BRAIN DAMAGE
-----------------
-
-This section describes some of the unfortunate and avoidable aspects
-of working with the Nios CPU ... and some things you can do to
-reduce your pain.
-
-6.1 GERMS doesn't work with Hyperterminal
-------------------------------------------
-GERMS doesn't do CR/LF mapping that is compatible with Hyperterminal
-(or minicom) -- geez. Regardless of you opion of Hyperterminal, this
-sad design decision is remedied by using U-Boot.
-
-6.2 cygwin Incompatibility
----------------------------
-The version of cygwin distributed with the nios GNUPro toolchain is
-out-of-date and incompatible with the latest cygwin distributions.
-In addition, many of the standard utilities are very dated as well.
-If you try to download and build the lastest version of grep for
-example, you'll quickly realize that a native gcc is not available
-(the next topic) which leads to U-Boot build problems (following
-topic).
-
-The solution ... well, you can wait for Altera ... or build as
-set of tools for linux.
-
-6.3 No native gcc
-------------------
-I'm not sure how this one slipped through the cracks ... but it is
-a real pain. Basically, if you want to build anything for the native
-environment -- forget it! A native (cygwin) gcc is not distributed,
-and the old version of cygwin makes locating one challenging.
-
-The solution ... same as above. Just download the gcc source from
-Altera and build up a set of cross tools for your favorite linux
-distro. Anybody who wants to use an already precompiled NIOS cross
-toolchain can it found in the CDK4NIOS project hosted by Source
-Forge at http://cdk4nios.sourceforge.net.
-
-6.4 Can't build default U-Boot
--------------------------------
-By default, when you build U-Boot you will be building some native
-tools along with the target elf, bin, and srec files. Without a
-native gcc, this (obviously) causes problems.
-
-For developers using the Altera cygwin tools you can remove the
-'tools' directory from SUBDIRS in the top-level Makefile. You will
-also have to edit common/Makefile:
-
-Replace:
-env_embedded.o: env_embedded.c ../tools/envcrc
- $(CC) $(AFLAGS) -Wa,--no-warn \
- -DENV_CRC=$(shell ../tools/envcrc) \
- -c -o $@ env_embedded.c
-
-With:
-env_embedded.o: env_embedded.c
- $(CC) $(AFLAGS) -Wa,--no-warn \
- -DENV_CRC=0 \
- -c -o $@ env_embedded.c
-
-BTW, thats a 'zero' ... not the letter 'O'. And not that the
-"../tools/envcrc" dependency is removed.
-
-
-7. HELP WANTED
----------------
-
-There are plenty of areas where help is needed. Here's are some ideas
-for those interested in contributing:
-
--CompactFlash. Port & test CF/FAT.
-
--Bedbug. Develop bedbug for Nios ... or at least provide a disassemble
- command.
-
--Add boot support for ucLinux (niosnommu).
-
--Implement (don't copy Altera code) the __mulxx routines using the
- MSTEP and MUL instructions (e.g. CONFIG_SYS_NIOS_MULT_HW and CONFIG_SYS_NIOS_MULT_MSTEP).
-
-
-Regards,
-
---Scott
-<smcnutt@psyent.com>
-
---Stephan
-<linz@li-pro.net>