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From:   Greentime Hu <green.hu@gmail.com>
Date:   Fri, 17 Nov 2017 21:50:43 +0800
Message-ID: <CAEbi=3en6GQBHLLYOqeKZc3AX5mbPbto-M0beK86DLT=U2+YDg@mail.gmail.com>
Subject: Re: [PATCH 26/31] nds32: Build infrastructure
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Greentime <greentime@andestech.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Networking <netdev@vger.kernel.org>,
        Vincent Chen <vincentc@andestech.com>
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2017-11-17 20:50 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
> On Fri, Nov 17, 2017 at 1:39 PM, Greentime Hu <green.hu@gmail.com> wrote:
>> 2017-11-10 16:26 GMT+08:00 Greentime Hu <green.hu@gmail.com>:
>>> 2017-11-09 18:33 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
>>>> On Thu, Nov 9, 2017 at 10:02 AM, Greentime Hu <green.hu@gmail.com> wrote:
>>>>> 2017-11-08 18:16 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
>>>>>> On Wed, Nov 8, 2017 at 6:55 AM, Greentime Hu <green.hu@gmail.com> 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.

Thanks. I got you.

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