linux-kernel - Re: [PATCH 1/3] time/sched_clock: Export sched_clock

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Date:   Wed, 8 Feb 2023 20:45:15 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        walter.chang@...iatek.com,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        "Maciej W . Rozycki" <macro@...am.me.uk>,
        John Stultz <jstultz@...gle.com>
Cc:     wsd_upstream@...iatek.com, stanley.chu@...iatek.com,
        Chun-hung.Wu@...iatek.com, Freddy.Hsin@...iatek.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 1/3] time/sched_clock: Export sched_clock_register()

On 08/02/2023 20:41, Matthias Brugger wrote:
> 
> 
> On 08/02/2023 15:24, Krzysztof Kozlowski wrote:
>> On 08/02/2023 10:48, walter.chang@...iatek.com wrote:
>>> From: Chun-Hung Wu <chun-hung.wu@...iatek.com>
>>>
>>> clocksource driver may use sched_clock_register()
>>> to resigter itself as a sched_clock source.
>>> Export it to support building such driver
>>> as module, like timer-mediatek.c
>>>
>>> Signed-off-by: Chun-Hung Wu <chun-hung.wu@...iatek.com>
>>> ---
>>>   kernel/time/sched_clock.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
>>> index 8464c5acc913..8e49e87d1221 100644
>>> --- a/kernel/time/sched_clock.c
>>> +++ b/kernel/time/sched_clock.c
>>> @@ -150,8 +150,7 @@ static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)
>>>   	return HRTIMER_RESTART;
>>>   }
>>>   
>>> -void __init
>>> -sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
>>> +void sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
>>
>> Is there a non-init caller?
>>
>>>   {
>>>   	u64 res, wrap, new_mask, new_epoch, cyc, ns;
>>>   	u32 new_mult, new_shift;
>>> @@ -223,6 +222,7 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
>>>   
>>>   	pr_debug("Registered %pS as sched_clock source\n", read);
>>>   }
>>> +EXPORT_SYMBOL_GPL(sched_clock_register);
>>
>> Where is the module using it?
>>
>> You need to bring users of these two changes, not just prepare something
>> for your out of tree patches.
>>
> 
> I'd propose to add at least one driver that will need these changes, to make it 
> clear why you need that.

... and actually test if the system works fine when booted from such
clocksource as a module. I have doubts that and unfortunately folks
working on GKI like to put whatever stuff from mainline into modules
even if it does not make sense for us (see long time ago discussion
about pinctrl drivers).

Best regards,
Krzysztof