xiaoxiang781216 commented on code in PR #9962:
URL: https://github.com/apache/nuttx/pull/9962#discussion_r1280146021
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sched/init/nx_start.c:
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@@ -698,10 +698,12 @@ void nx_start(void)
/* When control is return to this point, the system is idle. */
sinfo("CPU0: Beginning Idle Loop\n");
+#ifndef CONFIG_DISABLE_IDLE_LOOP
for (; ; )
{
/* Perform any processor-specific idle state operations */
up_idle();
}
+#endif
Review Comment:
this is because JLINK expect SEGGER_FL_Prepare return and halt CPU to download the image to SRAM, here is the basic workflow:
1. JLINK download nuttx image(contained ofloader) to SRAM through JTAG/SWD
2. JLINK control CPU to run SEGGER_FL_Prepare through JTAG/SWD
3. SEGGER_FL_Prepare call __start and then nx_start->nx_bringup
https://github.com/apache/nuttx-apps/pull/1872/files#diff-54269319ce436252f01744417956400103da2e849e0c59472fde9239886fee6cR187
4. nx_bringup create nsh_main task
5. nsh create ofloader task from /etc/init/rcS
https://github.com/apache/nuttx-apps/pull/1872/files#diff-662f0aa2ce979fda9fa2f94b8e5000208c1f2c6dc8047c8cd81a8f4f00da909cR309
6. When the initialization finish, idle thread call up_idle in an infinite loop
Without this change, SEGGER_FL_Prepare never return, and then JLINK can't start to download the image we want to flash.
With this change, SEGGER_FL_Prepare return, JLINK halt the CPU and download the image through JTAG/SWD, and jump to SEGGER_FL_Program:
https://github.com/apache/nuttx-apps/pull/1872/files#diff-54269319ce436252f01744417956400103da2e849e0c59472fde9239886fee6cR200
SEGGER_FL_Program wake up ofloader task to do the real program.
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