linux-kernel - Re: [PATCHv5 2/3] ARM: Allow machines to override _

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Date:	Thu, 7 Apr 2011 09:30:15 +0200
From:	Mattias Wallin <mattias.wallin@...ricsson.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCHv5 2/3] ARM: Allow machines to override __delay()

On 04/06/2011 01:56 AM, Stephen Boyd wrote:
> Some machines want to implement their own __delay() routine based
> on fixed rate timers. Expose functionality to set the __delay()
> routine at runtime. This should allow two machines with different
> __delay() routines to happily co-exist within the same kernel
> with minimal overhead.
>
> Russell expressed concern that using a timer based __delay()
> would cause problems when an iomapped device isn't mapped in
> prior to a delay call being made (see
> http://article.gmane.org/gmane.linux.ports.arm.kernel/78543  for
> more info). We can sidestep that issue with this approach since
> the __delay() routine_should_  only be pointed to a timer based
> delay once the timer has been properly mapped. Up until that
> point __delay() and udelay() will use delay_loop() which is
> always safe to call.
>
> This patch is inspired by x86's delay.c
>

Tested-by: Mattias Wallin <mattias.wallin@...ricsson.com>

Yours,
Mattias Wallin

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