linux-kernel - Re: [PATCH] ARC: Fix _

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Message-ID: <C2D7FE5348E1B147BCA15975FBA23075140F85@IN01WEMBXA.internal.synopsys.com>
Date:	Thu, 29 Aug 2013 06:49:07 +0000
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Joe Perches <joe@...ches.com>
CC:	Mischa Jonker <Mischa.Jonker@...opsys.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Joern Rennecke <joern.rennecke@...ecosm.com>
Subject: Re: [PATCH] ARC: Fix __udelay parentheses

On 08/29/2013 12:07 PM, Joe Perches wrote:
>> On the topic of multiply vs. divide (which probably is not relevant to topic at
>> hand though), since ARCompact doesn't have native divide, we end up emulating it
>> using libgcc routines. That makes it slightly non-deterministic (not a big deal)
>> and also adds to boot time (which those delays sprinkled all over the place in
>> crazy device probes and such). Seriously we got hammered by a customer for that once.
> That argues more for reducing the uses of hard delays
> than making the hard delay count calculation simpler.

Right, but most often the drivers are written/maintained by non arch people.

I'm with you in terms of simplification and I think the following

loops = ((u64)usecs * 4295 * HZ * loops_per_jiffy) >> 32;

is fairly simple, well commented, and optimal for ARC.

-Vineet
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