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

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Message-Id: <201306211612.15508.arnd@arndb.de>
Date:	Fri, 21 Jun 2013 16:12:15 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Tomasz Figa <t.figa@...sung.com>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	"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>,
	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 Friday 21 June 2013, Tomasz Figa wrote:

> > 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.
> 
> Well, it doesn't really give us any functional benefits.
> 
> However in my opinion it looks much saner in case of DT-only platforms that 
> don't need any specific IRQ initialization, but need to call some platform 
> specific initialization routines, after memory management, but before 
> anything else is initialized.
> 
> This way irqchip_init() doesn't have to be explicitly called in platform 
> code.
> 
> Anyway, I don't have any strong opinion on this. If it is perfectly fine to 
> abuse irqchip_init() for anything that must be done at this stage of boot, 
> then I'm fine with this either and will modify the board file from further 
> patch from this series to not rely on this change any more.

Your init_platform only has these two calls in it:

+       of_clk_init(NULL);
+       samsung_wdt_reset_of_init();

Presumably you need of_clk_init() for the watchdog to work. But do you actually
need to initialize the reset logic this early? Why not turn
samsung_wdt_reset_of_init into a standalone driver, or call it from init_machine?

I would actually like to call of_clk_init from common code at some point
between init_irq and init_time, although I'm not sure if some platforms
need it to be called before init_irq.

	Arnd
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