Re: [PATCH] [v2] Documentation: document ktime_get_*() APIs

[Arnd Bergmann]

On Fri, Jul 13, 2018 at 9:24 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Tue, Jul 10, 2018 at 4:48 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>>
>> Cc: Dave Chinner <david@xxxxxxxxxxxxx>
>> Cc: John Stultz <john.stultz@xxxxxxxxxx>
>> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> Cc: Stephen Boyd <sboyd@xxxxxxxxxx>
>> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
>> Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>> Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>> ---
>> v2: minor changes suggested by Randy
>
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Thanks!

> This brings into question commit bc2b7dab629a5
> "iio:core: timestamping clock selection support"
> that has bothered me for some time. Now that is ABI, but
> we might be able to do some recommendations based on the
> time base and have a sensible default moving forward.
>
> As I want to make that clock base parsing similar for GPIO
> I first thought it was a good idea to support the same clocks,
> but now it seems like a bad idea.
>
> IIRC you told me to simply hammer down the clock that
> makes the most sense.

Right, my general recommendation would be to return the
result of ktime_get_ns() in a __u64, since this does not suffer
from the settimeofday or leap second issues that clock_realtime
has, using the coarse clock to save 100 cycles per call probably
won't help.

       Arnd