linux-kernel - Re: [PATCH v2 -next] powerpc: kernel/time.c

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Date:   Wed, 24 Mar 2021 07:22:39 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        He Ying <heying24@...wei.com>
Cc:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        a.zummo@...ertech.it, npiggin@...il.com, msuchanek@...e.de,
        tglx@...utronix.de, peterz@...radead.org, geert+renesas@...der.be,
        kernelfans@...il.com, frederic@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-rtc@...r.kernel.org
Subject: Re: [PATCH v2 -next] powerpc: kernel/time.c - cleanup warnings



Le 24/03/2021 à 07:14, Christophe Leroy a écrit :
> 
> 
> Le 24/03/2021 à 00:05, Alexandre Belloni a écrit :
>> On 23/03/2021 23:18:17+0100, Alexandre Belloni wrote:
>>> Hello,
>>>
>>> On 23/03/2021 05:12:57-0400, He Ying wrote:
>>>> We found these warnings in arch/powerpc/kernel/time.c as follows:
>>>> warning: symbol 'decrementer_max' was not declared. Should it be static?
>>>> warning: symbol 'rtc_lock' was not declared. Should it be static?
>>>> warning: symbol 'dtl_consumer' was not declared. Should it be static?
>>>>
>>>> Declare 'decrementer_max' and 'rtc_lock' in powerpc asm/time.h.
>>>> Rename 'rtc_lock' in drviers/rtc/rtc-vr41xx.c to 'vr41xx_rtc_lock' to
>>>> avoid the conflict with the variable in powerpc asm/time.h.
>>>> Move 'dtl_consumer' definition behind "include <asm/dtl.h>" because it
>>>> is declared there.
>>>>
>>>> Reported-by: Hulk Robot <hulkci@...wei.com>
>>>> Signed-off-by: He Ying <heying24@...wei.com>
>>>> ---
>>>> v2:
>>>> - Instead of including linux/mc146818rtc.h in powerpc kernel/time.c, declare
>>>>    rtc_lock in powerpc asm/time.h.
>>>>
>>>
>>> V1 was actually the correct thing to do. rtc_lock is there exactly
>>> because chrp and maple are using mc146818 compatible RTCs. This is then
>>> useful because then drivers/char/nvram.c is enabled. The proper fix
>>> would be to scrap all of that and use rtc-cmos for those platforms as
>>> this drives the RTC properly and exposes the NVRAM for the mc146818.
>>>
>>> Or at least, if there are no users for the char/nvram driver on those
>>> two platforms, remove the spinlock and stop enabling CONFIG_NVRAM or
>>> more likely rename the symbol as it seems to be abused by both chrp and
>>> powermac.
>>>
>>
>> Ok so rtc_lock is not even used by the char/nvram.c driver as it is
>> completely compiled out.
>>
>> I guess it is fine having it move to the individual platform as looking
>> very quickly at the Kconfig, it is not possible to select both
>> simultaneously. Tentative patch:
>>
> 
> Looking at it once more, it looks like including linux/mc146818rtc.h is the thing to do, at least 
> for now. Several platforms are defining the rtc_lock exactly the same way as powerpc does, and 
> including mc146818rtc.h
> 
> I think that to get it clean, this change should go in a dedicated patch and do a bit more and 
> explain exactly what is being do and why. I'll try to draft something for it.
> 
> He Y., can you make a version v3 of your patch excluding the rtc_lock change ?
> 

Finally, I think there is not enough changes to justify a separate patch.

So you can send a V3 based on your V1. In addition to the changes you had in V1, please remove the 
declaration of rfc_lock in arch/powerpc/platforms/chrp/chrp.h

Christophe