After watchdog reset (for example, to enter reprogramming), the AVR core
restarts with watchdog enabled, contrary to a cold start after power on.
The C program is not given an opportunity to disable or reset the watchdog
before "main" ; and when the data and/or bss section is large enough, the
watchdog triggers a CPU reset during __do_copy_data or __do_clear_bss, and the
main therefore never starts.
To avoid this, I've added watchdog reset instructions in the __do_copy_data and
__do_clear_bss loops. Here is a patch :
*** gcc-4.5-20100311.orig/gcc/config/avr/libgcc.S 2009-05-23
09:16:07.000000000 +0200
--- gcc-4.5-20100311/gcc/config/avr/libgcc.S 2010-05-11 16:30:29.000000000
+0200
***************
*** 710,715 ****
--- 710,716 ----
out __RAMPZ__, r16
rjmp .L__do_copy_data_start
.L__do_copy_data_loop:
+ wdr /* Avoid watchdog reset if active */
elpm r0, Z+
st X+, r0
.L__do_copy_data_start:
***************
*** 728,733 ****
--- 729,735 ----
out __RAMPZ__, r16
rjmp .L__do_copy_data_start
.L__do_copy_data_loop:
+ wdr /* Avoid watchdog reset if active */
elpm
st X+, r0
adiw r30, 1
***************
*** 744,749 ****
--- 746,752 ----
ldi r31, hi8(__data_load_start)
rjmp .L__do_copy_data_start
.L__do_copy_data_loop:
+ wdr /* Avoid watchdog reset if active */
#if defined (__AVR_HAVE_LPMX__)
lpm r0, Z+
#else
***************
*** 769,774 ****
--- 772,778 ----
ldi r27, hi8(__bss_start)
rjmp .do_clear_bss_start
.do_clear_bss_loop:
+ wdr /* Avoid watchdog reset if active */
st X+, __zero_reg__
.do_clear_bss_start:
cpi r26, lo8(__bss_end)
--
Summary: AVR watchdog resets the core during initialization
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: j-etienne at users dot sourceforge dot net
GCC build triplet: x86_64-apple-darwin10.2.0
GCC host triplet: x86_64-apple-darwin10.2.0
GCC target triplet: avr-unknown-none
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44082
