linux-kernel - Re: [PATCH 3/3] clk: divider: fix calculation of initial best divider when rounding to closest

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Date:	Mon, 23 Feb 2015 10:42:12 +0100
From:	Maxime Coquelin <maxime.coquelin@...com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	<linux-kernel@...r.kernel.org>, <kernel@...gutronix.de>
Subject: Re: [PATCH 3/3] clk: divider: fix calculation of initial best divider
 when rounding to closest

Hi Uwe,

On 02/21/2015 11:40 AM, Uwe Kleine-König wrote:
> Similar to the reasoning for the previous commit
>
> 	DIV_ROUND_CLOSEST(parent_rate, rate)
>
> might not be the best integer divisor to get a good approximation for
> rate from parent_rate (given the metric for CLK_DIVIDER_ROUND_CLOSEST).
>
> For example assume a parent rate of 1000 Hz and a target rate of 700.
> Using DIV_ROUND_CLOSEST the suggested divisor gets calculated to 1
> resulting in a target rate of 1000 with a delta of 300 to the desired
> rate. With choosing 2 as divisor however the resulting rate is 500 which
> is nearer to 700.
>
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> ---
>   drivers/clk/clk-divider.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
>

This is correct. Thanks for fixing this.

You can add my:
Acked-by: Maxime Coquelin <maxime.coquelin@...com>


Best regards,
Maxime
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