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Re: [PATCH 0/4] clock: Get rid of clock_get_ns()
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH 0/4] clock: Get rid of clock_get_ns() |
Date: |
Fri, 11 Dec 2020 14:50:50 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 |
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.
- Re: [PATCH 1/4] clock: Introduce clock_ticks_to_ns(), (continued)