linux-kernel - Re: [PATCH, RFC 2/8] ARM: twd: register clock event for 1 core SMP

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Message-ID: <20130219121400.GP23197@arwen.pp.htv.fi>
Date:	Tue, 19 Feb 2013 14:14:00 +0200
From:	Felipe Balbi <balbi@...com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
CC:	Afzal Mohammed <afzal@...com>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<devicetree-discuss@...ts.ozlabs.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>,
	Marc Zyngier <marc.zyngier@....com>,
	Nicolas Pitre <nico@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Landley <rob@...dley.net>, Sekhar Nori <nsekhar@...com>,
	Syed Mohammed Khasim <khasim@...com>
Subject: Re: [PATCH, RFC 2/8] ARM: twd: register clock event for 1 core SMP

On Tue, Feb 19, 2013 at 03:44:14PM +0530, Santosh Shilimkar wrote:
> On Monday 18 February 2013 05:07 PM, Afzal Mohammed wrote:
> >Register percpu local timer for scheduler tick in the case of one core
> >SMP configuration. In other cases - secondary cpu's as well as boot
> >cpu's having more than one core, this is being registered as per
> >existing boot flow, with a difference that they happens after delay
> >calibration. Registering the clock for tick in case of one core should
> >be done before Kernel calibrates delay (this is required to boot,
> >unless local timer is the only one registered for tick). Registering
> >twd local timer at init_time (which platforms are doing now) helps
> >achieve that with the proposed change.
> >
> >This helps in an almost booting Kernel (minimal) by only relying on
> >ARM parts for an A9 one core SMP.
> >
> >Signed-off-by: Afzal Mohammed <afzal@...com>
> >---
> As mentioned in cover-letter, I don't think we have good
> reasoning to make TWD to work with UP configuration. Even
> you fix the timer code, there are more cascaded dependencies
> which is not worth the effort.

if CONFIG_SMP_ON_UP is enabled, smp_twd.c can still be compiled, right ?

-- 
balbi

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