Re: [PATCH 0/4] clock: Get rid of clock_get_ns()

[Philippe Mathieu-Daudé]

On 12/8/20 7:15 PM, Peter Maydell wrote:
> This patchseries makes some changes to the clock API:
>  * Remove clock_get_ns()
>  * Add clock_ticks_to_ns() to return number of nanoseconds
>    it will take the clock to tick N times
>  * clock_display_freq() to return prettily-formatted string
>    for showing humans the approximate clock frequency
> 
> This is based on discussions we had about these APIs a little while
> back.  The core driver here is that the clock objects internally
> store the period in units of 2^-32 ns, so both clock_get_ns() and
> clock_get_hz() are inherently returning a rounded-off result, which
> can be badly inaccurate for fast clocks or if you want to multiply it
> by a large tick count.
> 
> Ideally I'd like to get rid of clock_get_hz() as well, but
> that looks trickier than handling clock_get_ns().
> 
> Patch 4 borrows a lot of the concept from one of Philippe's that he
> sent out previously.

Thanks for tackling the clock_get_ns() part. I had some work in
progress I was procrastinating for after the release, but your
patches are much better documented :)

(I also started to get rid of clock_get_hz() but, as you figured,
this is not a trivial task).

> NB: tested with 'make check' and 'make check-acceptance' only.

I hit this issue while testing Huacai's MIPS Loongson3 virt machine
which sets the core freq at 1GHz IIRC. I still have the branch
so I'll test your series (or v2) during the week-end.

Regards,

Phil.