Re: [ECOS] Cortex M3 idle sleep

[Simon Kallweit <simon dot kallweit at intefo dot ch>]

Nick Garnett wrote:
> Simon Kallweit <simon.kallweit@intefo.ch> writes:
>
>   
> > Hello
> >
> > Would it make sense to include support for sleeping ("wfi"
> > instruction) in idle thread for the cortex m3 architecture? The
> > current code in hal_arch.h looks like:
> >
> > #if 0 //ndef HAL_IDLE_THREAD_ACTION
> > #define HAL_IDLE_THREAD_ACTION(__count) __asm__ volatile ( "wfi\n" )
> > #else
> > #define HAL_IDLE_THREAD_ACTION(__count) CYG_EMPTY_STATEMENT
> > #endif
> >
> > I guess this is not what it was meant to be. I would propose to add an option like CYGHWR_HAL_CORTEXM_IDLE_SLEEP to enable the wfi instruction:
> >
> > #ifndef HAL_IDLE_THREAD_ACTION
> > # ifdef CYGHWR_HAL_CORTEXM_IDLE_SLEEP
> > #  define HAL_IDLE_THREAD_ACTION(__count) __asm__ volatile ( "wfi\n" )
> > # else
> > #  define HAL_IDLE_THREAD_ACTION(__count) CYG_EMPTY_STATEMENT
> > # endif
> > #endif
> >
> > Also, currently var_arch.h gets not included in the hal_arch.h header, so it's impossible to override for example the HAL_IDLE_THREAD_ACTION macro. I guess this was just overlooked, or is it intentional?
> >
> > I can provide a patch if there are no objections.
> >     
>
>
> The "#if 0" is an oversight on my part. When debugging via JTAG I was
> having difficulties breaking in to an idle system. Stopping it using
> WFI solved this. The #else part is also a consequence of this, so that
> code should really be:
>   

Well that's actually the reason for me to propose a 
CYGHWR_HAL_CORTEXM_IDLE_SLEEP configuration option. During debugging, 
wfi is rather troublesome, so I thought it might be a good idea to make 
it configurable. Or is this too much cruft?

Simon

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