linux-kernel - Re: [PATCH] clocksource: tegra: wrap arch/arm-specific sections in CONFIG

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Message-ID: <54AFD9DF.9090205@linaro.org>
Date:	Fri, 09 Jan 2015 14:38:39 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Paul Walmsley <paul@...an.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-tegra@...r.kernel.org, Allen Martin <amartin@...dia.com>,
	Stephen Warren <swarren@...dia.com>,
	Thierry Reding <treding@...dia.com>,
	Alexandre Courbot <gnurou@...il.com>, pwalmsley@...dia.com
Subject: Re: [PATCH] clocksource: tegra: wrap arch/arm-specific sections in
 CONFIG_ARM

On 01/09/2015 02:33 PM, Thierry Reding wrote:
> On Fri, Jan 09, 2015 at 02:24:24PM +0100, Daniel Lezcano wrote:
>> On 01/09/2015 01:21 PM, Thierry Reding wrote:
>>> On Fri, Jan 09, 2015 at 09:31:08AM +0100, Daniel Lezcano wrote:
>>>> On 01/09/2015 03:09 AM, Paul Walmsley wrote:
>>>>> Hello Daniel
>>>>>
>>>>> On Thu, 8 Jan 2015, Daniel Lezcano wrote:
>>>>>
>>>>>> On 12/09/2014 11:07 PM, Paul Walmsley wrote:
>>>>>>>
>>>>>>> Like several of the other files in drivers/clocksource,
>>>>>>> tegra20_timer.c contains code that can only compile when CONFIG_ARM is
>>>>>>> enabled.  This causes obvious problems when trying to compile this
>>>>>>> code for NVIDIA ARM64-based SoCs, such as Tegra132.  The same timer IP
>>>>>>> blocks exist, so it seems appropriate to provide support for them.
>>>>>>>
>>>>>>> So until we figure out a better way to partition this code, wrap the
>>>>>>> delay_timer and persistent_clock support code with preprocessor tests
>>>>>>> for CONFIG_ARM.
>>>>>>>
>>>>>>>   (The delay_timer code should not be needed at all on
>>>>>>> ARM64 due to the presence of the ARMv8 architected timer.  The
>>>>>>> persistent_clock support code could become important once power
>>>>>>> management modes are implemented that turn off the CPU complex.)
>>>>>>
>>>>>> IIUC, the cpuidle driver is not yet ready, right ?
>>>>>>
>>>>>> If it is the case, this driver is not needed yet, no ?
>>>>>
>>>>> The point of the patch is to allow the hardware drivers selected by
>>>>> CONFIG_ARCH_TEGRA to build for an arm64 kernel, just as they build for
>>>>> 32-bit ARM.
>>>>>
>>>>> There's nothing CPUIdle-specific about the patch - that is, this timer can
>>>>> be selected as a clockevent and clocksource provider without the use of
>>>>> CPUIdle - although low-power PM idle is likely to be a primary use-case.
>>>>
>>>> What I meant is this timer is not needed for the moment.
>>>>
>>>>>> Perhaps you can rework a bit this driver in the meantime to have a better fix
>>>>>> than disabling the code with macros ?
>>>>>
>>>>> I'm happy to do that, but it would be nice to get the driver compiling
>>>>> first for ARM64 :-)
>>>>>
>>>>>> Otherwise, please try at least to group the code into a minimal set of macros.
>>>>>
>>>>> So, would it be accurate to say that you would prefer a patch that changes
>>>>> more lines of code, but minimizes preprocessor directives, to the current
>>>>> patch?
>>>>
>>>> Yes at least an attempt to factor out a bit the driver. Those #ifdef are
>>>> like #if 0, which is a quick fix. I am not strongly against this patch, but
>>>> it would be nice to take the opportunity to reorganize it a bit.
>>>
>>> How about we do something like the attached patch instead for now. That
>>> avoids any #ifdef'ery and still we don't attempt (and fail) to build the
>>> driver on 64-bit ARM.
>>>
>>> With that applied we can incrementally make the changes to untangle the
>>> ARM-specific parts and when the driver can build on 64-bit ARM we simply
>>> select TEGRA_TIMER via Kconfig.
>>
>> Yes, that is exactly what I was thinking about after sending the previous
>> email. And by this way, you also fixed the Kconfig option selection logic.
>
> Great. Will you give your Acked-by so that I can take that patch through
> the Tegra tree to resolve the build dependency?

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>


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