On Fri, Nov 17, 2017 at 1:39 PM, Greentime Hu <green.hu@xxxxxxxxx> wrote:
> 2017-11-10 16:26 GMT+08:00 Greentime Hu <green.hu@xxxxxxxxx>:
>> 2017-11-09 18:33 GMT+08:00 Arnd Bergmann <arnd@xxxxxxxx>:
>>> On Thu, Nov 9, 2017 at 10:02 AM, Greentime Hu <green.hu@xxxxxxxxx> wrote:
>>>> 2017-11-08 18:16 GMT+08:00 Arnd Bergmann <arnd@xxxxxxxx>:
>>>>> On Wed, Nov 8, 2017 at 6:55 AM, Greentime Hu <green.hu@xxxxxxxxx> wrote:
>>>
>>>>>> +config GENERIC_CALIBRATE_DELAY
>>>>>> + def_bool y
>>>>>
>>>>> It's better to avoid the delay loop completely and skip the calibration,
>>>>> if your hardware allows.
>>>>
>>>> Thanks.
>>>> Do you mean that this config should be def_bool n?
>>>> why? Almost all arch enable it.
>>>
>>> It depends on what your hardware can do. If you have a way to see how much
>>> time has passed that is guaranteed to be reliable on all machines, then
>>> use that instead.
>>>
>>> On a lot of architectures, it's not possible, so they have to fall back to using
>>> the delay loop.
>>
>> I get it. I will discuss it with our HW colleagues.
>> We may get these informations in some registers.
>
> Hi, Arnd:
>
> I think I can't set it to default n because it will be called in start_kernel.
>
> start_kernel() -> calibrate_delay()
>
> If I don't enable this config, it will link error because it didn't
> build init/calibrate.c
You will have to provide an architecture-specific implementation of
this function, please ahve a look at what others are doing, e.g. tile,
openrisc or
h8300.
Arnd
