| |
| 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> |