linux-kernel - Re: [PATCH v6 4/8] ARM: Add .init_platform() callback to machine descriptor

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Date:	Fri, 21 Jun 2013 11:24:52 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Tomasz Figa <tomasz.figa@...il.com>
CC:	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Mark Brown <broonie@...nel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Benoit Cousson <benoit.cousson@...aro.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Jason Cooper <jason@...edaemon.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Nicolas Pitre <nico@...xnic.net>,
	Russell King <linux@....linux.org.uk>,
	Stephen Warren <swarren@...dotorg.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <Will.Deacon@....com>
Subject: Re: [PATCH v6 4/8] ARM: Add .init_platform() callback to machine
 descriptor

On 21/06/13 01:35, Tomasz Figa wrote:

Hi Tomasz,

> Most ARM platforms have parts that should be initialized as early as
> possible, which usually means as soon as memory management (kmalloc,
> ioremap) starts to work,
> 
> However, currently there is no appropriate callback in machine_desc
> struct to use for such initialization and platforms tend to stuff things
> up .init_irq() and .init_time() callbacks.
> 
> Since all the DT-based platforms are going towards generic IRQ and time
> initialization (using irqchip_init and clocksource_of_init) and current
> code assumes that if custom callbacks are not provided in machine_desc
> then generic ones should be used, this problem has become a bit more
> inconvenient.
> 
> This patch tries to solve this issue by introducing new callback called
> .init_platform(), where any custom low level initialization of platform
> can be done safely.
> 
> Signed-off-by: Tomasz Figa <tomasz.figa@...il.com>
> ---
>  arch/arm/include/asm/mach/arch.h | 1 +
>  arch/arm/kernel/irq.c            | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
> index 308ad7d..b2f4d11 100644
> --- a/arch/arm/include/asm/mach/arch.h
> +++ b/arch/arm/include/asm/mach/arch.h
> @@ -46,6 +46,7 @@ struct machine_desc {
>  	void			(*reserve)(void);/* reserve mem blocks	*/
>  	void			(*map_io)(void);/* IO mapping function	*/
>  	void			(*init_early)(void);
> +	void			(*init_platform)(void);
>  	void			(*init_irq)(void);
>  	void			(*init_time)(void);
>  	void			(*init_machine)(void);
> diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
> index 9723d17..61e2000 100644
> --- a/arch/arm/kernel/irq.c
> +++ b/arch/arm/kernel/irq.c
> @@ -115,6 +115,9 @@ EXPORT_SYMBOL_GPL(set_irq_flags);
>  
>  void __init init_IRQ(void)
>  {
> +	if (machine_desc->init_platform)
> +		machine_desc->init_platform();
> +
>  	if (IS_ENABLED(CONFIG_OF) && !machine_desc->init_irq)
>  		irqchip_init();
>  	else

To me, this new hook is strictly equivalent to init_irq. What do we gain
exactly? I didn't think init_irq was going away...

I know init_irq is not pretty, and we tend to overload it with other
stuff, but I don't really see the point of adding a new callback that
has the exact same properties.

	M.
-- 
Jazz is not dead. It just smells funny...

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