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From: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>
To: "Lothar Waßmann" <LW-AvR2QvxeiV7DiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>
Cc: Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Fabio Estevam
	<fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org>,
	linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] i2c: mxs: fix broken timing calculation
Date: Fri, 5 Jul 2013 18:53:45 +0200	[thread overview]
Message-ID: <201307051853.45786.marex@denx.de> (raw)
In-Reply-To: <1373041680-26939-1-git-send-email-LW-bxm8fMRDkQLDiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>

Hi Lothar,

> The timing calculation is rather bogus and gives extremely wrong
> results for higher frequencies (on an i.MX28). E.g. instead of 400 kHz
> I measured 770 kHz.
> 
> Implement a calculation that adheres to the I2C spec and gives exact
> results for I2C frequencies from 12.56 kHz to 960 kHz.
> 
> Also the bus_free and leadin parameters are programmed according to
> the I2C spec for standard and fast mode.

I suspect the resulting speed is heavily dependent on hardware properties of the 
bus. Did you have a chance to check it with a scope? I will try to recheck on 
other boards next week.

Best regards,
Marek Vasut

  parent reply	other threads:[~2013-07-05 16:53 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-05 16:28 [PATCH] i2c: mxs: fix broken timing calculation Lothar Waßmann
     [not found] ` <1373041680-26939-1-git-send-email-LW-bxm8fMRDkQLDiMYJYoSAnRvVK+yQ3ZXh@public.gmane.org>
2013-07-05 16:53   ` Marek Vasut [this message]
     [not found]     ` <201307051853.45786.marex-ynQEQJNshbs@public.gmane.org>
2013-07-05 17:28       ` Lothar Waßmann
     [not found]         ` <20951.550.818976.677404-VjFSrY7JcPWvSplVBqRQBQ@public.gmane.org>
2013-07-05 17:37           ` Marek Vasut
     [not found]             ` <201307051937.10975.marex-ynQEQJNshbs@public.gmane.org>
2013-07-15 10:22               ` Lothar Waßmann
     [not found]                 ` <20963.52588.898163.953695-VjFSrY7JcPWvSplVBqRQBQ@public.gmane.org>
2013-07-15 12:24                   ` Marek Vasut
     [not found]                     ` <201307151424.32248.marex-ynQEQJNshbs@public.gmane.org>
2013-07-16  8:10                       ` Lothar Waßmann
     [not found]                         ` <20965.3.293494.346855-VjFSrY7JcPWvSplVBqRQBQ@public.gmane.org>
2013-07-17 17:54                           ` Marek Vasut
     [not found]                             ` <201307171954.59556.marex-ynQEQJNshbs@public.gmane.org>
2013-07-18 11:18                               ` Lothar Waßmann
     [not found]                                 ` <20967.53016.902909.282346-VjFSrY7JcPWvSplVBqRQBQ@public.gmane.org>
2013-08-15 10:12                                   ` Wolfram Sang
2013-08-15 10:13                                     ` Wolfram Sang
2013-08-15 21:30                                     ` Marek Vasut
2013-08-16 16:10   ` Wolfram Sang

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