On Thu, Jan 31, 2019 at 10:40 AM Simon Horman
<horms+renesas@xxxxxxxxxxxx> wrote:
> Support Z and Z2 clocks with parent frequencies greater than
> UINT32_MAX Hz (~4.29GHz).
>
> The DIV_ROUND_CLOSEST_ULL() macro accepts a 64bit numerator and 32bit
> denominator. This leads to truncation of the numerator, which is the Z or
> Z2 parent clock frequency in HZ, on platforms where frequency of that clock
> is greater than UINT32_MAX Hz.
>
> To resolve this problem the DIV_ROUND_CLOSEST() macro, which accepts the
> prevailing types of the numerator and denominator, is used. In this case
> the type of the numerator is unsigned long long (64 bit) and the type of
> the denominator is unsigned long (64bit on 64bit platforms and 32bit on
> 32bit platforms). This allows parents whose frequency is greater than
> UINT32_MAX Hz on 64bit platforms.
>
> This appears to be sufficient as this driver is only intended for use
> on 64bit systems. And in particular, the motivation for this change is
> to allow a 4.8GHz clock on the R-Car Gen3 E3 (r8a77990) SoC which is
> a 64bit platform.
>
> Signed-off-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
