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From: Wolfram Sang <wsa@the-dreams.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Linux I2C <linux-i2c@vger.kernel.org>,
	Linux-sh list <linux-sh@vger.kernel.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	Simon Horman <horms@verge.net.au>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Subject: Re: [RFC 5/9] i2c: rcar: honor additional i2c timings from DT
Date: Thu, 3 Dec 2015 11:59:00 +0100	[thread overview]
Message-ID: <20151203105900.GC1545@katana> (raw)
In-Reply-To: <CAMuHMdU1fWjH2Lv00W2uxRW7-XGp1YaEoA4Ftq5o6yk6WamCBQ@mail.gmail.com>

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Hi Geert,

> > -       round = (ick + 500000) / 1000000 * 285;
> > +       sum = t->scl_fall_ns + t->scl_rise_ns + t->scl_int_delay_ns;
> > +       round = (ick + 500000) / 1000000 * sum;
> 
> If you're sure it cannot overflow, doing the "* sum" before the division
> improves accuracy.

Thanks for the input. In this patch, however, I intentionally did not
change the formula but only replaced the constants with the now user
supplied values. Everything else should be a separate patch IMO.


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WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa@the-dreams.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Linux I2C <linux-i2c@vger.kernel.org>,
	Linux-sh list <linux-sh@vger.kernel.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	Simon Horman <horms@verge.net.au>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Subject: Re: [RFC 5/9] i2c: rcar: honor additional i2c timings from DT
Date: Thu, 03 Dec 2015 10:59:00 +0000	[thread overview]
Message-ID: <20151203105900.GC1545@katana> (raw)
In-Reply-To: <CAMuHMdU1fWjH2Lv00W2uxRW7-XGp1YaEoA4Ftq5o6yk6WamCBQ@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 506 bytes --]

Hi Geert,

> > -       round = (ick + 500000) / 1000000 * 285;
> > +       sum = t->scl_fall_ns + t->scl_rise_ns + t->scl_int_delay_ns;
> > +       round = (ick + 500000) / 1000000 * sum;
> 
> If you're sure it cannot overflow, doing the "* sum" before the division
> improves accuracy.

Thanks for the input. In this patch, however, I intentionally did not
change the formula but only replaced the constants with the now user
supplied values. Everything else should be a separate patch IMO.


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  reply	other threads:[~2015-12-03 10:59 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-26 22:59 [RFC 0/9] i2c: add generic support for timing parameters Wolfram Sang
2015-11-26 22:59 ` Wolfram Sang
2015-11-26 22:59 ` [RFC 1/9] i2c: document generic DT bindings " Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-26 22:59 ` [RFC 2/9] i2c: add generic routine to parse DT timing information Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-26 22:59 ` [RFC 3/9] i2c: rcar: refactor probe function a little Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-26 22:59 ` [RFC 4/9] i2c: rcar: switch to i2c generic dt parsing Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-26 22:59 ` [RFC 5/9] i2c: rcar: honor additional i2c timings from DT Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-27  8:04   ` Geert Uytterhoeven
2015-11-27  8:04     ` Geert Uytterhoeven
2015-12-03 10:59     ` Wolfram Sang [this message]
2015-12-03 10:59       ` Wolfram Sang
2015-11-26 22:59 ` [RFC 6/9] ARM: shmobile: r8a7790: dtsi: add internal delay for i2c IPs Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-26 22:59 ` [RFC 7/9] ARM: shmobile: r8a7791: " Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-27 11:58   ` Sergei Shtylyov
2015-11-27 11:58     ` Sergei Shtylyov
2015-11-26 22:59 ` [RFC 8/9] ARM: shmobile: r8a7794: " Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang
2015-11-26 22:59 ` [RFC 9/9] arm64: renesas: r8a7795: " Wolfram Sang
2015-11-26 22:59   ` Wolfram Sang

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