Re: [PATCH] hw/timer/armv7m_systick: Update clock source before enabling timer

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 1 Feb 2022 at 19:28, Richard Petri <git@rpls.de> wrote:
>
> Starting the SysTick timer and changing the clock source a the same time
> will result in an error, if the previous clock period was zero. For exmaple,
> on the mps2-tz platforms, no refclk is present. Right after reset, the
> configured ptimer period is zero, and trying to enabling it will turn it off
> right away. E.g., code running on the platform setting
>
>     SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk;
>
> should change the clock source and enable the timer on real hardware, but
> resulted in an error in qemu.
>
> Signed-off-by: Richard Petri <git@rpls.de>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Thanks, you've saved me a debugging session! I had a bug report about
a problem with the systick timer a couple of days back, but I hadn't yet
got round to investigating it, and now I don't have to, because this
patch fixes the reported failure :-)

-- PMM