Message-ID: <37721084ba1145097fc0dcbb8d74acb7@localhost>
Date:	Tue, 20 Aug 2013 08:11:37 +0200
From:	<b.brezillon@...rkiz.com>
To:	Nicolas Ferre <nicolas.ferre@...el.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Richard Genoud <richard.genoud@...il.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Russell King <linux@....linux.org.uk>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/8] ARM: at91: move peripheral id definitions to
 dt-bindings include dir

Hello Nicolas,

On Mon, 19 Aug 2013 18:46:13 +0200, Nicolas Ferre
<nicolas.ferre@...el.com> wrote:
> On 08/08/2013 06:09, boris brezillon :
>> Hello Arnd,
>>
>> On 07/08/2013 22:24, Arnd Bergmann wrote:
>>> On Thursday 01 August 2013, Boris BREZILLON wrote:
>>>> This patch moves peripheral id definitions from machine specific include
>>>> dir (arch/arm/mach-at91/include/mach/'soc-name'.h) to dt-bindinds include
>>>> dir (include/dt-bindings/at91/'soc-name'/peripherals.h).
>>>>
>>>> These definitions will be used inside dt to define interrupt ids and
>>>> peripheral clk ids.
>>>>
>>>> Signed-off-by: Boris BREZILLON <b.brezillon@...rkiz.com>
>>> This seems counterproductive, why would you do that?
>>
>> This was requested by Jean-Christophe Plagniol-Villard (and proposed by
>> Richard Genoud)
>> for the 3rd version of the "ARM: at91: move to common clk framework"
>> patch series (see
>> https://lkml.org/lkml/2013/7/29/361) and thought it was a good idea too
>> (even if I didn't know
>> where to put the macro files as there are no soc specific macro files in
>> dt-bindings include
>> dir).
>>
>> Indeed I found it much easier to detect bugs in dt definition using
>> macros because
>> the macro names and dt node names are the same (it does not protect
>> against errors
>> in the macro definitions).
>>
>> If you think these macro definitions should be dropped, I won't argue
>> against this.
>> But please, have a talk with Jean-Christophe first.
> 
> [..]
> 
>>> There is no sharing of identifiers across SoCs here, you just move the
>>> data around, and changing the .dts files to use the abstract macros would
>>> just end up making them harder to understand, not easier, since you then
>>> have to look up the numbers in another file.
> 
> Boris, Jean-Christophe and Richard,
> 
> Well, I must say that I do agree with Arnd on this point.
> 
> I think that a simple numeric field in a cell has to be represented
> as a number and even if this simple information is used twice
> (interrupt number and clock bit position in PMC). The possibility of
> error is very low compared to the big amount of unneeded definitions
> added by this solution.
> 
> Moreover, I had the hope to completely remove this long list of
> peripheral definitions for all SoC when we have a full DT kernel (with
> your patches about common clock framework). So I think it is not
> interesting to move in this direction and continue to build such a
> list for future full DT products...
> 
> Believe me, I am sorry that I didn't entered the discussion earlier
> and avoid unnecessary work... Anyway, give me your opinion, but I do
> think that the simpler is the best.
> 

As discussed with you (on IRC), I am not absolutely convinced we need
these macro definitions, and given the direction you want to take
(completely
remove the peripheral id definitions), i would say we'd rather drop
this patch.
It won't bother me at all to rework the "sama5 dt clk" patch series
(this is the
only SoC I supported in the 3rd version of the at91 common clk
transition)
to remove references to these macros.

Best Regards,
Boris

> Bye,

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