Re: [Qemu-devel] [Qemu devel v5 PATCH 0/5] Add support for Smartfusion2 SoC

[sundeep subbaraya]

Hi Peter,

On Mon, Jul 3, 2017 at 2:30 AM, Peter Maydell <address@hidden>
wrote:

> On 2 July 2017 at 18:39, sundeep subbaraya <address@hidden> wrote:
> > I figured out that systick uses cpu clock as clock source and
> > system_clock_scale
> > need to be set in msf2-soc.c. There is a bug in u-boot where it uses cpu
> > clock as
> > systick input but configures systick in external clock mode. I have
> tested
> > the modified
> > u-boot on real hardware too and it works fine. I am calculating
> > system_clock_scale
> > as below:
> > If CPU clock is X MHz then system_clock_scale = (1 / X) * 1000
> >
> > Tested with different frequencies and they are yielding same results.
>
> If you calculate it like that you'll probably get rounding
> errors. Better is
>   system_clock_scale = NANOSECONDS_PER_SECOND / freq_in_hz;
>
> (Our systick implementation hardwires the external clock
> frequency at 1MHz, but this is not really correct, it
> depends on the SoC.)
>

Ok. Modified as per your comment.

Thanks,
Sundeep

>
> thanks
> -- PMM
>