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-rw-r--r--doc/README.nios118
1 files changed, 109 insertions, 9 deletions
diff --git a/doc/README.nios b/doc/README.nios
index d3a9277..671e727 100644
--- a/doc/README.nios
+++ b/doc/README.nios
@@ -55,6 +55,12 @@ 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
----------------------------------
@@ -79,7 +85,11 @@ description).
CONFIG_NIOS -- defined for all Nios-32 boards.
-CFG_NIOS_CONSOLE -- the base address of the console UART.
+CFG_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).
CFG_NIOS_FIXEDBAUD -- defined if the console UART PTF fixed_baud
@@ -176,20 +186,109 @@ GERMS monitor (that is, avoid running code stored in flash memory):
3. Release CFG_NIOS_CPU_BUTTON_PIO, button number 0.
-5. BRAIN DAMAGE
+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 cpu/nios
+ (gdb) directory lib_nios
+ (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.
-5.1 GERMS doesn't work with Hyperterminal
+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.
-5.2 cygwin Incompatibility
+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.
@@ -202,7 +301,7 @@ topic).
The solution ... well, you can wait for Altera ... or build as
set of tools for linux.
-5.3 No native gcc
+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
@@ -215,7 +314,7 @@ 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
+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
@@ -232,15 +331,16 @@ environment.o: environment.c ../tools/envcrc
-c -o $@ environment.c
With:
-environment.o: environment.c ../tools/envcrc
+environment.o: environment.c
$(CC) $(AFLAGS) -Wa,--no-warn \
-DENV_CRC=0 \
-c -o $@ environment.c
-BTW, thats a 'zero' ... not the letter 'O'.
+BTW, thats a 'zero' ... not the letter 'O'. And not that the
+"../tools/envcrc" dependency is removed.
-6. HELP WANTED
+7. HELP WANTED
---------------
There are plenty of areas where help is needed. Here's are some ideas