Re: ISR/DSR without kernel present

[Bob Koninckx <bob dot koninckx at mech dot kuleuven dot ac dot be>]

On Wed, 2003-07-30 at 17:08, Nick Garnett wrote:
> Bob Koninckx <bob.koninckx@mech.kuleuven.ac.be> writes:
> 
> > Hi all,
> > 
> > It seems that all infrastructure to use ISR/DSR handling in systems
> > without a kernel is already present in drv-api.c. Some conditional
> > compiles however seem to prevent things from getting used. The attached
> > patches make Redboot handle interrupts flawlessly on the powerpc
> > platform.
> > 
> 
> These patches seem fine from the point of view of getting interrupts
> to work in non-kernel configurations. It was always intended that this
> be the case, but we have never had any applications to test it. So
> bitrot has set in.
> 
> However, I do question your desire to make RedBoot handle interrupts.
> RedBoot was explicitly designed to work with interrupts disabled since
> trying to debug code while interrupts are firing can be very hard, and
> depending on interrupts working in order to debug makes things very
> fragile. Also, most applications want to handle their own interrupts
> and will steal the interrupt vectors from RedBoot at startup.
> 
> So, what do you actually want RedBoot interrupts for?

Redboot is much more than just a debugger, isn't it ? I am implementing
a bootp like functionality on top of the CAN/CANopen fieldbus, allowing
our distributed motion controller to get its application software from
the CAN bus rather than from flash. Getting this operational without
interrupts might be possible but will certainly not be trivial.

After the application has booted there is no problem if it steals away
interrupts from redboot, we'll never return to it anyway. Also debugging
is no problem, we use BDM for that purpose.

Although I agree with your objections if you look at redboot primarily
as a debug monitor, I still think that there are arguments for using
interrupts, especially if you look at it as a bootloader.

As a sideline, using the hardware watchdog on the powerpc is near
impossible if you can not use interrupts in redboot. I had a discussion
with jifl on this subject not so long ago.

Thanks for reviewing the patches!

Bob

-- 
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ir. Bob Koninckx
Katholieke Universiteit Leuven
Division Production Engineering,                   tel.  +32 16 322535
Machine Design and Automation                      fax.  +32 16 322987
Celestijnenlaan 300B                  bob.koninckx@mech.kuleuven.ac.be
B-3001 Leuven Belgium               http://www.mech.kuleuven.ac.be/pma
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