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From: Trent Piepho <tpiepho@impinj.com>
To: "andy.shevchenko@gmail.com" <andy.shevchenko@gmail.com>,
	"hayashibara.keiji@socionext.com"
	<hayashibara.keiji@socionext.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"masami.hiramatsu@linaro.org" <masami.hiramatsu@linaro.org>,
	"hayashi.kunihiko@socionext.com" <hayashi.kunihiko@socionext.com>,
	"broonie@kernel.org" <broonie@kernel.org>,
	"mark.rutland@arm.com" <mark.rutland@arm.com>,
	"linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
	"yamada.masahiro@socionext.com" <yamada.masahiro@socionext.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"jaswinder.singh@linaro.org" <jaswinder.singh@linaro.org>
Subject: Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
Date: Thu, 26 Jul 2018 17:01:36 +0000	[thread overview]
Message-ID: <1532624495.2283.197.camel@impinj.com> (raw)
In-Reply-To: <CAHp75VcEdxDEo0T5_9BzOPaeaqjbmbrWmaE9+ZuUDYhjh6jpVw@mail.gmail.com>

On Thu, 2018-07-26 at 11:46 +0300, Andy Shevchenko wrote:
> > +
> > +       /*
> > +        * the supported rates are even numbers from 4 to 254. (4,6,8...254)
> > +        * round up as we look for equal or less speed
> > +        */
> > +       ckrat = DIV_ROUND_UP(clk_get_rate(priv->clk), speed);
> > +       ckrat = roundup(ckrat, 2);
> 
> ckrat += ckrat & 1;

Either way, the compiler produces the same code:

 add r0, r0, #1
 bic r0, r0, #1

I.e., ckrat = (ckrat + 1) & ~1, one "add" and one "and".

Might as well use the macro so it's clear. There is also round_up(x,y),
which I believe is intended to be used only with power of 2 values of
y.

WARNING: multiple messages have this Message-ID (diff)
From: tpiepho@impinj.com (Trent Piepho)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
Date: Thu, 26 Jul 2018 17:01:36 +0000	[thread overview]
Message-ID: <1532624495.2283.197.camel@impinj.com> (raw)
In-Reply-To: <CAHp75VcEdxDEo0T5_9BzOPaeaqjbmbrWmaE9+ZuUDYhjh6jpVw@mail.gmail.com>

On Thu, 2018-07-26 at 11:46 +0300, Andy Shevchenko wrote:
> > +
> > +       /*
> > +        * the supported rates are even numbers from 4 to 254. (4,6,8...254)
> > +        * round up as we look for equal or less speed
> > +        */
> > +       ckrat = DIV_ROUND_UP(clk_get_rate(priv->clk), speed);
> > +       ckrat = roundup(ckrat, 2);
> 
> ckrat += ckrat & 1;

Either way, the compiler produces the same code:

 add r0, r0, #1
 bic r0, r0, #1

I.e., ckrat = (ckrat + 1) & ~1, one "add" and one "and".

Might as well use the macro so it's clear. There is also round_up(x,y),
which I believe is intended to be used only with power of 2 values of
y.

  parent reply	other threads:[~2018-07-26 17:01 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-26  7:09 [PATCH v2 0/2] add SPI controller driver for UniPhier SoCs Keiji Hayashibara
2018-07-26  7:09 ` Keiji Hayashibara
2018-07-26  7:09 ` [PATCH v2 1/2] dt-bindings: spi: add DT bindings for UniPhier SPI controller Keiji Hayashibara
2018-07-26  7:09   ` Keiji Hayashibara
2018-07-30 21:47   ` Rob Herring
2018-07-30 21:47     ` Rob Herring
2018-07-30 23:44     ` Keiji Hayashibara
2018-07-30 23:44       ` Keiji Hayashibara
2018-07-26  7:09 ` [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC Keiji Hayashibara
2018-07-26  7:09   ` Keiji Hayashibara
2018-07-26  8:46   ` Andy Shevchenko
2018-07-26  8:46     ` Andy Shevchenko
2018-07-26  9:38     ` Keiji Hayashibara
2018-07-26  9:38       ` Keiji Hayashibara
2018-07-26 10:57       ` Radu Pirea
2018-07-26 10:57         ` Radu Pirea
2018-07-30  1:15         ` Keiji Hayashibara
2018-07-30  1:15           ` Keiji Hayashibara
2018-07-30  1:15           ` Keiji Hayashibara
2018-07-26 13:44       ` Andy Shevchenko
2018-07-26 13:44         ` Andy Shevchenko
2018-07-30  1:46         ` Keiji Hayashibara
2018-07-30  1:46           ` Keiji Hayashibara
2018-07-26 17:01     ` Trent Piepho [this message]
2018-07-26 17:01       ` Trent Piepho
2018-07-26 17:01       ` Trent Piepho
2018-07-30  5:30       ` Keiji Hayashibara
2018-07-30  5:30         ` Keiji Hayashibara
2018-07-30  5:30         ` Keiji Hayashibara
2018-07-30  8:39         ` Andy Shevchenko
2018-07-30  8:39           ` Andy Shevchenko
2018-07-26  9:12   ` Masahiro Yamada
2018-07-26  9:12     ` Masahiro Yamada
2018-07-26  9:49     ` Keiji Hayashibara
2018-07-26  9:49       ` Keiji Hayashibara

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