linux-kernel - Re: [RFC PATCH 2/5] clk: Introduce 'clk_round_rate

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Message-ID: <20140520075158.GK16662@pengutronix.de>
Date:	Tue, 20 May 2014 09:51:58 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Michal Simek <michal.simek@...inx.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 2/5] clk: Introduce 'clk_round_rate_nearest()'

Hello,

On Mon, May 19, 2014 at 10:29:05AM -0700, Sören Brinkmann wrote:
> With the improvements suggested by you I have this now:
> 
> long clk_round_rate_nearest(struct clk *clk, unsigned long rate)
> {
> 	unsigned long lower, upper;
> 
> 	lower = clk_round_rate(clk, rate);
> 	if (lower >= rate)
> 		return lower;
> 
> 	upper = clk_round_rate(clk, rate + (rate - lower) - 1);
> 	if (upper == lower)
> 		return upper;
> 
> 	lower = rate + 1;
> 	while (lower < upper) {
> 		unsigned long rounded, mid;
> 
> 		mid = lower + ((upper - lower) >> 1);
> 		rounded = clk_round_rate(clk, mid);
> 		if (rounded < lower)
> 			lower = mid + 1;
> 		else
> 			upper = rounded;
> 	}
> 
> 	return upper;
> }
This is nearly my version now. I just lacks the overflow check when
calculating upper and I skipped the early return if (upper == lower).
(Instead the while condition evaluates to false on the first hit and
returns with the same result.)

Other than that I added a few comments. :-)

Something we still should resolve is the return type. It should match
clk_round_rate, but should both be signed or unsigned? 

Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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