linux-kernel - Re: [PATCH] arm: Fix linux-next compile error in arch/arm/common/gic.c

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Message-ID: <4F03085F.4060008@gmail.com>
Date:	Tue, 03 Jan 2012 07:53:35 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Marc Zyngier <marc.zyngier@....com>
CC:	Yang Bai <hamo.by@...il.com>, Joerg Roedel <joerg.roedel@....com>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] arm: Fix linux-next compile error in arch/arm/common/gic.c



On 01/03/2012 05:16 AM, Marc Zyngier wrote:
> [Adding Will to the loop as he's the author of the logical map stuff,
> though I'm not sure he'll read that before next week...]
> 
> On 03/01/12 00:44, Yang Bai wrote:
>> On Tue, Jan 3, 2012 at 12:33 AM, Joerg Roedel <joerg.roedel@....com> wrote:
>>> With CONFIG_SMP=n the following compile error occurs:
>>>
>>>  CC      arch/arm/common/gic.o
>>> arch/arm/common/gic.c: In function 'gic_init_bases':
>>> arch/arm/common/gic.c:679:4: error: implicit declaration of function 'cpu_logical_map' [-Werror=implicit-function-declaration]
>>> cc1: some warnings being treated as errors
>>>
>>> This patch fixes the problem.
>>>
>>> Cc: Marc Zyngier <marc.zyngier@....com>
>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
>>> Cc: Rob Herring <rob.herring@...xeda.com>
>>> Cc: linux-arm-kernel@...ts.infradead.org
>>> Cc: linux-kernel@...r.kernel.org
>>> Signed-off-by: Joerg Roedel <joerg.roedel@....com>
>>> ---
>>>  arch/arm/common/gic.c |    5 ++++-
>>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
>>> index b2dc2dd..b33f6b0 100644
>>> --- a/arch/arm/common/gic.c
>>> +++ b/arch/arm/common/gic.c
>>> @@ -676,7 +676,10 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
>>>                }
>>>
>>>                for_each_possible_cpu(cpu) {
>>> -                       unsigned long offset = percpu_offset * cpu_logical_map(cpu);
>>> +                       unsigned long offset = percpu_offset;
>>> +#ifdef CONFIG_SMP
>>> +                       offset *= cpu_logical_map(cpu);
>>> +#endif
>>>                        *per_cpu_ptr(gic->dist_base.percpu_base, cpu) = dist_base + offset;
>>>                        *per_cpu_ptr(gic->cpu_base.percpu_base, cpu) = cpu_base + offset;
>>>                }
>>> --
>>> 1.7.5.4
>>>
>>>
>>
>> Is this the right way to fix it? Or shall we do like this:
>>
>> #ifdef CONFIG_SMP
>> ...
>> #else
>> #define cpu_logical_map() 1
>> #endif
>>
>> and leave the gic.c code unchanged.

IIRC, part of the problem is asm/smp.h is only included by linux/smp.h
for CONFIG_SMP, so this would have to change. Doing that could easily
break other arches.

> 
> Well, both patches are wrong. In the UP case (and assuming we're running
> on physical CPU 0), offset should be 0.
> 
> The second patch would be my favorite approach, except that
> cpu_logical_map(x) should return either "x" or 0. And I'm not sure how
> to handle the (unlikely?) case of running a UP kernel on a secondary CPU...

Wouldn't this be the case with 2 AMP instances of Linux running?

Rob


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