| |
| 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. |
| |
| |
| 2. CONFIGURATION OPTIONS/SETTINGS |
| ---------------------------------- |
| |
| 2.1 Nios-specific Options/Settings |
| ----------------------------------- |
| All configuration options/settings that are specific to Nios begin |
| with "CONFIG_NIOS_", "CFG_NIOS_", or "CFG_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 "CFG_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. |
| |
| CFG_NIOS_CONSOLE -- the base address of the console UART. |
| (standard-32: nasys_uart_0 resp. na_uart1_base). |
| |
| CFG_NIOS_FIXEDBAUD -- defined if the console UART PTF fixed_baud |
| parameter is set to '1'. |
| |
| CFG_NIOS_MULT_HW -- use full hardware multiply (not yet implemented). |
| |
| CFG_NIOS_MULT_MSTEP -- use hardware assisted multiply using the |
| MSTEP instruction (not yet implemented). |
| |
| CFG_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). |
| |
| CFG_NIOS_TMRIRQ -- the interrupt request (vector number) assigned to |
| the timer. (standard-32: nasys_timer_1_irq resp. |
| na_low_priority_timer2_irq). |
| |
| CFG_NIOS_TMRMS -- the period of the timer in milliseconds. |
| |
| CFG_NIOS_TMRCNT -- the preloadable counter value for the timer if it has |
| no fixed period. |
| |
| CFG_NIOS_ASMIBASE -- the base address of the ASMI peripheral. |
| (standard-32: na_asmi_base). |
| |
| CFG_NIOS_SPIBASE -- the base address of the SPI master (!) peripheral. |
| (nasys_spi_0) |
| |
| CFG_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. |
| |
| CFG_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 CFG_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 CFG_NIOS_CPU_FLASH_BASE + 0x04000C. |
| 2. Examining the button 0 on the PIO CFG_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 |
| CFG_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 CFG_NIOS_CPU_BUTTON_PIO, button number 0. |
| 2. Press then release the CPU reset button. |
| 3. Release CFG_NIOS_CPU_BUTTON_PIO, button number 0. |
| |
| |
| 5. 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. |
| |
| 5.1 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. |
| |
| 5.2 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. |
| |
| 5.3 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. |
| |
| 5.4 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: |
| environment.o: environment.c ../tools/envcrc |
| $(CC) $(AFLAGS) -Wa,--no-warn \ |
| -DENV_CRC=$(shell ../tools/envcrc) \ |
| -c -o $@ environment.c |
| |
| With: |
| environment.o: environment.c ../tools/envcrc |
| $(CC) $(AFLAGS) -Wa,--no-warn \ |
| -DENV_CRC=0 \ |
| -c -o $@ environment.c |
| |
| BTW, thats a 'zero' ... not the letter 'O'. |
| |
| |
| 6. 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. CFG_NIOS_MULT_HW and CFG_NIOS_MULT_MSTEP). |
| |
| |
| Regards, |
| |
| --Scott |
| <smcnutt@psyent.com> |
| |
| --Stephan |
| <linz@li-pro.net> |
