linux-kernel - Re: [RFC PATCH] clocksource: ti-32k: convert to platform device

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Message-ID: <5658B8B2.5030505@ti.com>
Date:	Fri, 27 Nov 2015 22:10:26 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Felipe Balbi <balbi@...com>, <linux@....linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Tony Lindgren <tony@...mide.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [RFC PATCH] clocksource: ti-32k: convert to platform device

Hi Felipe,

On 11/20/2015 08:21 PM, Felipe Balbi wrote:
> Grygorii Strashko <grygorii.strashko@...com> writes:
>> Since system clocksource is finally selected by Clocksource core at
>> fs_initcall stage during boot there are no reasons to initialize
>> ti_32k_timer at early boot stages. Hence, ti_32k_timer can be
>> converted to use platform device/driver model and its PM can be
>> implemented using PM runtime which is common for OMAP devices.
>>
>> Platform specific initialization code has to be disabled once as
>> ti_32k_timer is converted to platform device - otherwise OMAP platform
>> code will generate boot warnings.
>>
>> After this change, all counter_32k's platform code can be removed
>> once all OMAP boards will be converted to DT.
>>
>> Cc: Tony Lindgren <tony@...mide.com>
>> Cc: Felipe Balbi <balbi@...com>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>> ---

[...]

>> +
>> +static struct platform_driver ti_32k_driver __initdata = {
>> +	.probe		= ti_32k_probe,
>> +	.driver		= {
>> +		.name	= "ti_32k_timer",
>> +		.of_match_table = of_match_ptr(ti_32k_of_table),
>> +	}
>> +};
>> +
>> +static int __init ti_32k_init(void)
>> +{
>> +	return platform_driver_register(&ti_32k_driver);
>>   }
>> -CLOCKSOURCE_OF_DECLARE(ti_32k_timer, "ti,omap-counter32k",
>> -		ti_32k_timer_init);
>> +
>> +subsys_initcall(ti_32k_init);
>> +
>> +MODULE_AUTHOR("Paul Mundt");
>> +MODULE_AUTHOR("Juha Yrjölä");
>> +MODULE_DESCRIPTION("OMAP2 32k Timer");
>> +MODULE_ALIAS("platform:ti_32k_timer");
>> +MODULE_LICENSE("GPL v2");
> 
> this will break clksource_of_init(), right ? Eventually, we want that to
> be the only thing called by our .init_time method. I'll leave it to Tony
> to decide, but IMO this is not a good path forward for timers.
> 

Yeh :(.  I did additional tests, and, unfortunately, this can't be used as is.
But not because of clocksource_of_init() which will just produce boot warning.
It can't be done because of sched_clock_register() which is expected to be
called during early boot time only and with disabled IRQs.

It was so tempting to try :)
Thanks for your comment.

-- 
regards,
-grygorii
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