netdev - Re: [PATCH v5 1/3] clocksource/drivers/atcpit100: Add andestech atcpit100 timer

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Message-ID: <CAEbi=3c4yAx7Tejz8aPw3-3vj89t8cg-zNEY-vbF7KaMo8OM0Q@mail.gmail.com>
Date:   Thu, 4 Jan 2018 22:06:38 +0800
From:   Greentime Hu <green.hu@...il.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Greentime <greentime@...estech.com>,
        Rick Chen <rickchen36@...il.com>,
        Rick Chen <rick@...estech.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh+dt@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Vincent Chen <deanbo422@...il.com>,
        DTML <devicetree@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Will Deacon <will.deacon@....com>, linux-serial@...r.kernel.org
Subject: Re: [PATCH v5 1/3] clocksource/drivers/atcpit100: Add andestech
 atcpit100 timer

Hi, Daniel:

2018-01-04 21:50 GMT+08:00 Daniel Lezcano <daniel.lezcano@...aro.org>:
>
> Hi,
>
> sorry I missed your answer. Comments below.
>
> On 13/12/2017 07:06, Greentime Hu wrote:
>> Hi, Daniel:
>>
>> 2017-12-12 18:05 GMT+08:00 Daniel Lezcano <daniel.lezcano@...aro.org>:
>>> On 12/12/2017 06:46, Rick Chen wrote:
>>>> ATCPIT100 is often used on the Andes architecture,
>>>> This timer provide 4 PIT channels. Each PIT channel is a
>>>> multi-function timer, can be configured as 32,16,8 bit timers
>>>> or PWM as well.
>>>>
>>>> For system timer it will set channel 1 32-bit timer0 as clock
>>>> source and count downwards until underflow and restart again.
>>>
>>> [ ... ]
>>>
>>>> +config CLKSRC_ATCPIT100
>>>> +     bool "Clocksource for AE3XX platform"
>>>> +     depends on NDS32 || COMPILE_TEST
>>>> +     depends on HAS_IOMEM
>>>> +     help
>>>> +       This option enables support for the Andestech AE3XX platform timers.
>>>
>>> Hi Rick,
>>>
>>> the general rule for the Kconfig is:
>>>
>>> bool "Clocksource for AE3XX platform" if COMPILE_TEST
>>>
>>> and no deps on the platform.
>>>
>>> It is up to the platform Kconfig to select the option.
>>>
>>> We want here a silent option but make it selectable in case of
>>> compilation test coverage.
>>
>>
>> The way we like to use it is because
>> 1. This timer is a basic component to boot an nds32 CPU and it should
>> be able to select without COMPILE_TEST for nds32 architecture.
>
> Yes, so you don't need it to be selectable, you must select it from the
> platform's Kconfig.

I am not sure that I get your point or not.
We don't have a CONFIG_PLAT_AE3XX.
Do you mean we should create one and select CLKSRC_ATCPIT100 under
CONFIG_PLAT_AE3XX?

>> 2. It seems conflict with debug info. I am not sure if there is
>> another way to debug kernel(with debug info) with COMPILE_TEST and
>> DEBUG_INFO because we need this driver for nds32 architecture.
>>
>> Symbol: DEBUG_INFO [=n]
>> Type  : boolean
>> Prompt: Compile the kernel with debug info
>>   Location:
>>     -> Kernel hacking
>>       -> Compile-time checks and compiler options
>>   Defined at lib/Kconfig.debug:140
>>   Depends on: DEBUG_KERNEL [=y] && !COMPILE_TEST [=n]
>
> The COMPILE_TEST option is only there to allow cross-compilation test
> coverage, it does not select or unselect the driver in usual way.
>
> If the COMPILE_TEST is enabled, then the option will appear in the
> menuconfig, so that gives the opportunity to select/unselect it.
>
> Otherwise, the Kconfig's platform selects automatically the driver and
> the user *can't* unselect it from the menuconfig as it is a silent
> option and that is certainly what you want.
>
>>> Also, this driver is not a CLKSRC but a TIMER. Rename CLKSRC_ATCPIT100
>>> to TIMER_ATCPIT100.
>>
>> Thanks. We will rename it in the next version patch.
>
> You just resend an entire series V5 for the architecture. I'm confused,
> what is the merging path ?

Sorry. I didn't get your point.
We sent the timer patch and the architecture patch together because it
would be easier for reviewer to check the vdso implementations.
What do you mean about the merging path?

Thanks.