linux-kernel - Re: [PATCH 2/2] coresight: Adding coresight support to arm64

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Date:	Mon, 2 Feb 2015 15:06:16 -0700
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Will Deacon <will.deacon@....com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] coresight: Adding coresight support to arm64

On 2 February 2015 at 06:45, Will Deacon <will.deacon@....com> wrote:
> On Fri, Jan 30, 2015 at 10:54:26PM +0000, mathieu.poirier@...aro.org wrote:
>> From: Mathieu Poirier <mathieu.poirier@...aro.org>
>>
>> Aside from tracers, all currently supported coresight IP blocks
>> are 64 bit ready.  As such add the required symbol definition to
>> compile the framework and drivers.
>>
>> Also fixing a couple of warnings picked up by the 64bit compiler.
>>
>> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
>> ---
>>  arch/arm64/Kconfig.debug            | 48 +++++++++++++++++++++++++++++++++++++
>>  drivers/coresight/coresight-etb10.c |  2 +-
>>  drivers/coresight/coresight-tmc.c   |  2 +-
>>  3 files changed, 50 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
>> index 5fdd6dce8061..77dfebbcbffe 100644
>> --- a/arch/arm64/Kconfig.debug
>> +++ b/arch/arm64/Kconfig.debug
>> @@ -66,4 +66,52 @@ config DEBUG_SET_MODULE_RONX
>>            against certain classes of kernel exploits.
>>            If in doubt, say "N".
>>
>> +menuconfig CORESIGHT
>> +     bool "CoreSight Tracing Support"
>> +     select ARM_AMBA
>> +     help
>> +       This framework provides a kernel interface for the CoreSight debug
>> +       and trace drivers to register themselves with. It's intended to build
>> +       a topological view of the CoreSight components based on a DT
>> +       specification and configure the right serie of components when a
>> +       trace source gets enabled.
>
> Why does this need to be duplicated by each architecture wanting to make
> use of coresight capabilities defined under drivers/coresight? Can't we
> instead have this menuconfig and associated suboptions defined by a core
> Kconfig file, then have HAVE_ARCH_CORESIGHT_TRACE or something which can
> be selected by architectures wanting to make use of the framework?
>
> Will

"arch/arm/Kconfig.debug" and "arch/arm64/Kconfig.debug" already have a
fair amount of duplication so I wasn't sure if this is the approach
you guys wanted to take.  I agree that a common core Kconfig file
would make much more sense and I see a couple of ways to do this:

1) lib/Kconfig.debug being sourced by both arm/Kconfig.debug and
arm64/Kconfig.debug.  We can add a lib/Kconfig.coresight or
lib/Kconfig.arm and source them the same way.

2) Adding coresight entries to the Kconfig.debug made sense a while
back.  Maybe it is time to move them to drivers/coresight/Kconfig...
That way it would be easily accessible by both arm and arm64.

You may have ideas of your own too...

Thanks,
Mathieu
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