linux-kernel - Re: [RFC PATCH v2 2/2] drivers: mfd: vexpress: add Serial Power Controller (SPC) support

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Date:	Wed, 05 Jun 2013 17:32:30 +0100
From:	"Jon Medhurst (Tixy)" <tixy@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pawel Moll <pawel.moll@....com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Achin Gupta <achin.gupta@....com>,
	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
Subject: Re: [RFC PATCH v2 2/2] drivers: mfd: vexpress: add Serial Power
 Controller (SPC) support

On Wed, 2013-06-05 at 12:46 +0100, Lorenzo Pieralisi wrote:
[...]
> +
> +static bool __init __vexpress_spc_check_loaded(void);
> +static bool (*spc_check_loaded)(void) = &__vexpress_spc_check_loaded;

We get a section mismatch warning from the above because
__vexpress_spc_check_loaded is marked __init.

Now, we know the code is safe because we replace the reference in the
early_initcall below, before the init section is discarded (which is the
whole point of the construct) so we can add __refdata to the declaration
of spc_check_loaded to silence the warning.

Other than that I've not noticed any issues when testing the patches.

> +
> +static bool __init __vexpress_spc_check_loaded(void)
> +{
> +	if (vexpress_spc_load_result == -EAGAIN)
> +		vexpress_spc_load_result = vexpress_spc_init();
> +	spc_check_loaded = &vexpress_spc_initialized;
> +	return vexpress_spc_initialized();
> +}
> +
> +/*
> + * Function exported to manage early_initcall ordering.
> + * SPC code is needed very early in the boot process
> + * to bring CPUs out of reset and initialize power
> + * management back-end. After boot swap pointers to
> + * make the functionality check available to loadable
> + * modules, when early boot init functions have been
> + * already freed from kernel address space.
> + */
> +bool vexpress_spc_check_loaded(void)
> +{
> +	return spc_check_loaded();
> +}
> +EXPORT_SYMBOL_GPL(vexpress_spc_check_loaded);
> +
> +static int __init vexpress_spc_early_init(void)
> +{
> +	__vexpress_spc_check_loaded();
> +	return vexpress_spc_load_result;
> +}
> +early_initcall(vexpress_spc_early_init);
[...]

-- 
Tixy

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