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

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Message-ID: <CAMXH7KFYA24sPUcwgKfwVLNPA0jWQ-QG02y+SfPNnAqdiv0+gg@mail.gmail.com>
Date:	Tue, 17 Apr 2012 14:32:02 -0500
From:	Rob Lee <rob.lee@...aro.org>
To:	Sascha Hauer <s.hauer@...gutronix.de>
Cc:	kernel@...gutronix.de, linaro-dev@...ts.linaro.org,
	patches@...aro.org, daniel.lezcano@...aro.org,
	linux-kernel@...r.kernel.org, amit.kucheria@...aro.org,
	shawn.guo@...aro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] ARM: imx: Add common imx cpuidle init functionality.

>> >> +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.
>>
>> >> +
>> >> +void imx_cpuidle_devices_uninit(void)
>> >> +{
>> >> +     int cpu_id;
>> >> +     struct cpuidle_device *dev;
>> >> +
>> >> +     for_each_possible_cpu(cpu_id) {
>> >> +             dev = per_cpu_ptr(imx_cpuidle_devices, cpu_id);
>> >> +             cpuidle_unregister_device(dev);
>> >> +     }
>> >> +
>> >> +     free_percpu(imx_cpuidle_devices);
>> >> +}
>> >> +
>> >> +static int __init imx_cpuidle_init(void)
>> >
>> > ... instead of passing it directly to the function which uses it?
>> >
>>
>> 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.
>
> Just put the initcall into mm-imx5.c and check the cpu type. Then you
> also don't have to make imx5_idle global.

That solution is currently available for imx5 but for imx6q it implies
adding the cpu type support for imx6q.  Are you ok with that?

>
> Sascha
>
>
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