All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Keiji Hayashibara" <hayashibara.keiji@socionext.com>
To: "'Trent Piepho'" <tpiepho@impinj.com>, <andy.shevchenko@gmail.com>
Cc: linux-kernel@vger.kernel.org, robh+dt@kernel.org,
	devicetree@vger.kernel.org, masami.hiramatsu@linaro.org,
	"Hayashi, Kunihiko/林 邦彦" <hayashi.kunihiko@socionext.com>,
	broonie@kernel.org, mark.rutland@arm.com,
	linux-spi@vger.kernel.org, "Yamada,
	Masahiro/山田 真弘" <yamada.masahiro@socionext.com>,
	linux-arm-kernel@lists.infradead.org, jaswinder.singh@linaro.org
Subject: RE: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
Date: Mon, 30 Jul 2018 14:30:25 +0900	[thread overview]
Message-ID: <002901d427c6$6b9a4ff0$42ceefd0$@socionext.com> (raw)
In-Reply-To: <1532624495.2283.197.camel@impinj.com>

Hello Trent and Andy,

> From: Trent Piepho [mailto:tpiepho@impinj.com]
> Sent: Friday, July 27, 2018 2:02 AM
> To: andy.shevchenko@gmail.com; Hayashibara, Keiji/林原 啓二 <hayashibara.keiji@socionext.com>
> Subject: Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
> 
> 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.

I confirmed round_up() macro.
This macro is optimized to power of 2 argument,
and it matches to this case and clear.

I will replace to round_up() macro.

Thank you.

-----------------
Best Regards,
Keiji Hayashibara



WARNING: multiple messages have this Message-ID (diff)
From: "Keiji Hayashibara" <hayashibara.keiji@socionext.com>
To: 'Trent Piepho' <tpiepho@impinj.com>, andy.shevchenko@gmail.com
Cc: linux-kernel@vger.kernel.org, robh+dt@kernel.org,
	devicetree@vger.kernel.org, masami.hiramatsu@linaro.org,
	"Hayashi, Kunihiko/林 邦彦" <hayashi.kunihiko@socionext.com>,
	broonie@kernel.org, mark.rutland@arm.com,
	linux-spi@vger.kernel.org, "Yamada,
	Masahiro/山田 真弘" <yamada.masahiro@socionext.com>,
	linux-arm-kernel@lists.infradead.org, jaswinder.singh@linaro.org
Subject: RE: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
Date: Mon, 30 Jul 2018 14:30:25 +0900	[thread overview]
Message-ID: <002901d427c6$6b9a4ff0$42ceefd0$@socionext.com> (raw)
In-Reply-To: <1532624495.2283.197.camel@impinj.com>

Hello Trent and Andy,

> From: Trent Piepho [mailto:tpiepho@impinj.com]
> Sent: Friday, July 27, 2018 2:02 AM
> To: andy.shevchenko@gmail.com; Hayashibara, Keiji/林原 啓二 <hayashibara.keiji@socionext.com>
> Subject: Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
> 
> 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.

I confirmed round_up() macro.
This macro is optimized to power of 2 argument,
and it matches to this case and clear.

I will replace to round_up() macro.

Thank you.

-----------------
Best Regards,
Keiji Hayashibara

WARNING: multiple messages have this Message-ID (diff)
From: hayashibara.keiji@socionext.com (Keiji Hayashibara)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
Date: Mon, 30 Jul 2018 14:30:25 +0900	[thread overview]
Message-ID: <002901d427c6$6b9a4ff0$42ceefd0$@socionext.com> (raw)
In-Reply-To: <1532624495.2283.197.camel@impinj.com>

Hello Trent and Andy,

> From: Trent Piepho [mailto:tpiepho at impinj.com]
> Sent: Friday, July 27, 2018 2:02 AM
> To: andy.shevchenko at gmail.com; Hayashibara, Keiji/?? ?? <hayashibara.keiji@socionext.com>
> Subject: Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
> 
> 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.

I confirmed round_up() macro.
This macro is optimized to power of 2 argument,
and it matches to this case and clear.

I will replace to round_up() macro.

Thank you.

-----------------
Best Regards,
Keiji Hayashibara

  reply	other threads:[~2018-07-30  5:30 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
2018-07-26 17:01       ` Trent Piepho
2018-07-26 17:01       ` Trent Piepho
2018-07-30  5:30       ` Keiji Hayashibara [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='002901d427c6$6b9a4ff0$42ceefd0$@socionext.com' \
    --to=hayashibara.keiji@socionext.com \
    --cc=andy.shevchenko@gmail.com \
    --cc=broonie@kernel.org \
    --cc=devicetree@vger.kernel.org \
    --cc=hayashi.kunihiko@socionext.com \
    --cc=jaswinder.singh@linaro.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-spi@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=masami.hiramatsu@linaro.org \
    --cc=robh+dt@kernel.org \
    --cc=tpiepho@impinj.com \
    --cc=yamada.masahiro@socionext.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.