Re: [Qemu-trivial] [PATCH] hw/timer/armv7m_systick: Fix default system_clock_scale. Resolves SIGFPE divide by zero.

[Philippe Mathieu-Daudé]

Hi Domen,

Please have a look at the Contribute/SubmitAPatch guidelines for QEMU,
in particular about CC'ing the maintainers so your patch won't get lost:

https://wiki.qemu.org/Contribute/SubmitAPatch#CC_the_relevant_maintainer

$ ./scripts/get_maintainer.pl -f hw/timer/armv7m_systick.c
Peter Maydell <address@hidden> (maintainer:ARM cores)
address@hidden (open list:ARM cores)

^ Cc'ing them how.

On 11/01/2017 05:59 PM, Domen Puncer Kugler wrote:
> Fix default system_clock_scale. Resolves SIGFPE divide by zero.
> 
> Netduino platform code does not provide a way to set
> system_clock_scale, so it remains 0.
> This causes a divide by zero, when emulated code asks systick for
> current timer value:
>     (s->tick - (t + 1)) / systick_scale(s)) + 1;
> Patch fixes this by providing a default value.

See the thread around this reply:
http://lists.nongnu.org/archive/html/qemu-devel/2017-06/msg06678.html

> 
> Also replaces a magic number an with already defined constant:
>     #define SYSTICK_SCALE 1000ULL
> 
> 
> Signed-off-by: Domen Puncer Kugler <address@hidden>
> ---
> 
> diff --git a/hw/timer/armv7m_systick.c b/hw/timer/armv7m_systick.c
> index df8d2804b3..651f8030a8 100644
> --- a/hw/timer/armv7m_systick.c
> +++ b/hw/timer/armv7m_systick.c
> @@ -25,15 +25,15 @@
>  #define SYSTICK_CLKSOURCE (1 << 2)
>  #define SYSTICK_COUNTFLAG (1 << 16)
> 
> -int system_clock_scale;
> +uint64_t system_clock_scale = SYSTICK_SCALE;
> 
>  /* Conversion factor from qemu timer to SysTick frequencies.  */
> -static inline int64_t systick_scale(SysTickState *s)
> +static inline uint64_t systick_scale(SysTickState *s)
>  {
>      if (s->control & SYSTICK_CLKSOURCE) {
>          return system_clock_scale;
>      } else {
> -        return 1000;
> +        return SYSTICK_SCALE;
>      }
>  }
> 

Regards,

Phil.