linux-kernel - Re: [PATCH 05/21] atm: he: use mdelay instead of large udelay constants

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Message-ID: <20130426091220.468cf59e@thirdoffive.cmf.nrl.navy.mil>
Date:	Fri, 26 Apr 2013 09:12:20 -0400
From:	chas williams - CONTRACTOR <chas@....nrl.navy.mil>
To:	"David Laight" <David.Laight@...LAB.COM>
Cc:	"Arnd Bergmann" <arnd@...db.de>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-atm-general@...ts.sourceforge.net>, <netdev@...r.kernel.org>
Subject: Re: [PATCH 05/21] atm: he: use mdelay instead of large udelay
 constants

On Fri, 26 Apr 2013 09:21:59 +0100
"David Laight" <David.Laight@...LAB.COM> wrote:

> > ARM cannot handle udelay for more than 2 miliseconds, so we
> > should use mdelay instead for those.
> ...
> > @@ -1055,7 +1055,7 @@ static int he_start(struct atm_dev *dev)
> >  	he_writel(he_dev, 0x0, RESET_CNTL);
> >  	he_writel(he_dev, 0xff, RESET_CNTL);
> > 
> > -	udelay(16*1000);	/* 16 ms */
> > +	mdelay(16);	/* 16 ms */
> >  	status = he_readl(he_dev, RESET_CNTL);
> 
> 16ms seems a long time to spin.
> I'd have thought a sleep would be more appropriate.
> Since this looks like timing a hardware reset pulse
> it can't matter if it is somewhat longer.

Yes, I wrote this bit some time ago when I was less wise. The
programmer's guide doesn't say how long to sleep, so the value isn't
critical.  It just has to be "long enough".  An msleep() would be fine
here.
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