linux-kernel - Re: [PATCH 1/3] ARM: imx: Add common imx cpuidle init functionality.

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Message-ID: <CAMXH7KGNMFrv3HHjNYOokwQrEfEb7i1QJ1jwkwtLMLUYymefDw@mail.gmail.com>
Date:	Tue, 17 Apr 2012 09:32:11 -0500
From:	Rob Lee <rob.lee@...aro.org>
To:	Christian Robottom Reis <kiko@...aro.org>
Cc:	Sascha Hauer <s.hauer@...gutronix.de>, linaro-dev@...ts.linaro.org,
	patches@...aro.org, linux-kernel@...r.kernel.org,
	kernel@...gutronix.de, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] ARM: imx: Add common imx cpuidle init functionality.

On Tue, Apr 17, 2012 at 9:13 AM, Christian Robottom Reis
<kiko@...aro.org> wrote:
> On Tue, Apr 17, 2012 at 08:54:03AM -0500, Rob Lee wrote:
>> >> +void __init imx_cpuidle_set_driver(struct cpuidle_driver *p)
>> >> +{
>> >> +     drv = p;
>> >> +}
>> >
>> > You like it complicated, eh? Why do you introduce a function which sets
>> > a variable...
>>
>> This complication is used to deal with the timing of various levels of
>> init calls.  More explanation below.
>
> Regardless of how you end up solving this, it's probably a good idea
> to document the rationale, perhaps cribbing from what you describe
> below..

Agree.  Adding comments to the function itself seems to be the most
relevant location so I can add that information there if the function
remains.

>
>> If I called imx_cpuidle_init directly from imx5 or imx6q init
>> routines, it would be getting called before the coreinit_call of core
>> cpuidle causing a failure.  There were various other directions to
>> take and all seemed less desirable than this one.
>>
>> One alternative would be to add a function to return the pointer to
>> the cpuidle driver object based on the machine type.  Functionality
>> exists to identify imx5 as a machine type but not imx6q, so I couldn't
>> use that machine based method without adding that extra code.
>>
>> Another alternative would be to add a general platform lateinit_call
>> function to each platforms that support cpuidle.
>
> ..in a comment; without it, the code indeed looks bizarre.
> --
> Christian Robottom Reis, Engineering VP
> Brazil (GMT-3) | [+55] 16 9112 6430 | [+1] 612 216 4935
> Linaro.org: Open Source Software for ARM SoCs
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