[delete] INSTALL. refer to README

[fw/stlink] / README

diff --git a/README b/README
index 47c7c2f05e81bb47128f7fc15731cadb4d4de903..fbd75c10744bdcd50f663a24d02378029c825693 100644 (file)
--- a/README
+++ b/README
@@ -1,8 +1,14 @@
 HOWTO
 =====
 
-To run the gdb server, do (you do not need sudo if you have
-set up permissions correctly):
+First, load the sg kernel module.
+# modprobe sg
+
+On Ubuntu you need to install the package libsgutils2-dev:
+# sudo apt-get install libsgutils2-dev
+
+To run the gdb server, do (you do not need sudo if you have set up
+permissions correctly):
 $ make -C build && sudo ./build/st-util 1234 /dev/sg1
 
 Then, in gdb:
@@ -10,11 +16,38 @@ Then, in gdb:
 
 Have fun!
 
+Resetting the chip from GDB
+===========================
+
+You may reset the chip using GDB if you want. You'll need to use `target
+extended-remote' command like in this session:
+(gdb) target extended-remote localhost:1111
+Remote debugging using localhost:1111
+0x080007a8 in _startup ()
+(gdb) kill
+Kill the program being debugged? (y or n) y
+(gdb) run
+Starting program: /home/whitequark/ST/apps/bally/firmware.elf 
+
+Remember that you can shorten the commands. `tar ext :1111' is good enough
+for GDB.
+
+Setting up udev rules
+=====================
+
+For convenience, you may install udev rules file, 10-stlink.rules, located
+in the root of repository. You will need to copy it to /etc/udev/rules.d,
+and then either reboot or execute
+$ udevadm control --reload-rules
+
+Udev will now create a /dev/stlink file, which will point at appropriate
+/dev/sgX device. Good to not accidentally start debugging your flash drive.
+
 Running programs from SRAM
 ==========================
 
-You can run your firmware directly from SRAM if you want to.
-Just link it at 0x20000000 and do
+You can run your firmware directly from SRAM if you want to. Just link
+it at 0x20000000 and do
 (gdb) load firmware.elf
 
 It will be loaded, and pc will be adjusted to point to start of the
@@ -28,18 +61,20 @@ If you would link your executable to 0x08000000 and then do
 (gdb) load firmware.elf
 then it would be written to the memory.
 
-Caveats
-=======
+FAQ
+===
+
+Q: My breakpoints do not work at all or only work once.
 
-`continue' GDB command does not work: target does not step at
-all or steps with a turtle speed. Looks like there's something
-wrong with SCSI requests.
+A: Optimizations can cause severe instruction reordering. For example,
+if you are doing something like `REG = 0x100;' in a loop, the code may
+be split into two parts: loading 0x100 into some intermediate register
+and moving that value to REG. When you set up a breakpoint, GDB will
+hook to the first instruction, which may be called only once if there are
+enough unused registers. In my experience, -O3 causes that frequently.
 
-GDB sends requests for a multi-sectioned ELF files (most ones;
-having both .text and .rodata is enough) in a quite strange way which
-absolutely does not conform to flash page boundaries. Which is even more
-weird when you think about FlashErase requests which it sends correctly.
-And I couldn't think of a way which will resolve this correctly now.
+Q: At some point I use GDB command `next', and it hangs.
 
-Hardware breakpoints are not supported yet. You can still run your code from
-RAM, and then GDB will insert bkpt opcodes automagically.
+A: Sometimes when you will try to use GDB `next' command to skip a loop,
+it will use a rather inefficient single-stepping way of doing that.
+Set up a breakpoint manually in that case and do `continue'.