[PATCH v2 3/9] bsps/leon3: Make GPTIMER fall back mandatory

[Sebastian Huber]

Hello Martin,

On 13.10.23 12:09, Martin Åberg wrote:
> Hello Sebastian,
> 
> My understanding is that with this patch, one GPTIMER subtimer is always 
> allocated for the timecounter in uniprocessor configuration in the case 
> of "use_gptimer".

yes, exactly.

> 
> 
> Does this mean that the lower hardware requirement for all LEON3 systems 
> is raised to require a GPTIMER with two available subtimers?
> (Since the last hardware subtimer is typically dedicated to the watchdog 
> function, three subtimers would in practice be needed.)

Yes, but this requirement holds only for systems which do not provide an 
alternative free-running counter, such as the DSU time tag, IRQ(A)MP 
timestamp, %asr23, etc.

> 
> 
> What are the implications when using RTEMS_MULTIPROCESSING together with 
> "use_gptimer"?
> 
> In bsps/sparc/leon3/include/bsp/leon3.h, we have:
>  >  #if defined(RTEMS_MULTIPROCESSING)
>  >  #define LEON3_CLOCK_INDEX \
>  >    ( rtems_configuration_get_user_multiprocessing_table() ? 
> LEON3_Cpu_Index : 0 )
>  >  #else
>  >  #define LEON3_CLOCK_INDEX 0
>  >  #endif
> 
> Can LEON3_COUNTER_GPTIMER_INDEX of CPU0 be equal to LEON3_CLOCK_INDEX of 
> CPU1 here?

The individual RTEMS instances could share the GPTIMER configured in 
free-running mode.

The GR712RC and GR740 do not need the additional GPTIMER subtimer. Which 
products would be affected by this change? I hope that all future 
Gaisler products provide a free-running counter device with a capture 
feature for PPS.

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