Moffett, Kyle D wrote:
Hi!
On Mar 08, 2011, at 19:13, Scott McNutt wrote:
Hi Kyle,
Kyle Moffett wrote:
The Nios-II port appears to use no generic hardware capability for performing a CPU reset. Since all of the supported boards use the exact same code to perform a jump-to-flash it goes into __arch_restart().
This means that Nios-II has a no-op __arch_emergency_restart() function. If the CPU is in an invalid state then jump-to-FLASH probably won't work.
If the CPU state is stable enough to call __arch_emergency_restart(), a jump to the reset address should be fine. In many implementations the reset code is in on-chip ROM. If things get screwed up enough to affect the code in on-chip ROM, it probably won't matter what gets called. ;-)
... <snip> ...
Basically the emergency_restart() code should handle being called even in the following scenarios:
- Unexpected CPU exception or interrupt occurs
- Interrupts on or off, or *from* an interrupt or trap handler.
- FLASH or other peripherals in an undefined state
If that's the case for your onboard ROM then I will certainly remove the no-op emergency restart hook from this patch.
From a practical perspective, in the case of on-chip ROM, it would be no different than a hard reset during any of the above activities. But please don't remove it. Your position is sound and conservative.
I haven't had time to review the entire patch set yet. I'm assuming the __board_emergency_restart() routine is where a board can override the default arch-specific behavior? If so, you already provided the hooks for more daring developers. ;-)
Regards, --Scott