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

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Message-ID: <95cd80c5-40ff-1316-9c89-2e8e7836fb6a@csgroup.eu>
Date:   Wed, 24 Mar 2021 07:14:59 +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 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 ?

Christophe