From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Balbi Subject: Re: [PATCH] i2c: omap: highspeed only over 1000mhz Date: Mon, 20 Oct 2008 15:53:55 +0300 Message-ID: <20081020125355.GC31599@gandalf.research.nokia.com> References: <1224277795-17143-1-git-send-email-felipe.balbi@nokia.com> <20081020102659.GA31599@gandalf.research.nokia.com> <48FC7CA9.4040102@gmail.com> Reply-To: felipe.balbi@nokia.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from smtp.nokia.com ([192.100.105.134]:31619 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752080AbYJTMyj (ORCPT ); Mon, 20 Oct 2008 08:54:39 -0400 Content-Disposition: inline In-Reply-To: <48FC7CA9.4040102@gmail.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: ext Nishanth Menon Cc: felipe.balbi@nokia.com, linux-omap@vger.kernel.org, Ben Dooks , Tony Lindgren On Mon, Oct 20, 2008 at 07:42:17AM -0500, ext Nishanth Menon wrote: > Felipe, > Felipe Balbi said the following on 10/20/2008 05:26 AM: > > up to 1000khz it's Fast Mode+, not highspeed. > > > > Signed-off-by: Felipe Balbi > > --- > > drivers/i2c/busses/i2c-omap.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > > index a999606..53d6244 100644 > > --- a/drivers/i2c/busses/i2c-omap.c > > +++ b/drivers/i2c/busses/i2c-omap.c > > @@ -296,7 +296,7 @@ static int omap_i2c_init(struct omap_i2c_dev *dev) > > psc = psc - 1; > > > > /* If configured for High Speed */ > > - if (dev->speed > 400) { > > + if (dev->speed > 1000) { > > > Ref: http://www.nxp.com/acrobat_download/literature/9398/39340011.pdf > Page 4: > "Serial, 8-bit oriented, bi-directional data transfers can be > made at *up to* 100 kbit/s in the Standard-mode, *up to* > 400 kbit/s in the Fast-mode, or *up to* 3.4 Mbit/s in the > High-speed mode" > > Why do say high speed is >1000khz? http://www.standardics.nxp.com/support/documents/i2c/pdf/i2c.bus.specification.pdf section 5.2: "Fast-mode Plus (Fm+) devices offer an increase in I2C-bus transfer speeds and total bus capacitance. Fm+ devices can transfer information at bit rates of up to 1 Mbit/s, yet they remain fully downward compatible with Fast- or Standard-mode devices for bidirectional communication in a mixed-speed bus system. The same serial bus protocol and data format is maintained as with the Fast- or Standard-mode system. Fm+ devices also offer increased drive current over Fast- or Standard-mode devices allowing them to drive longer and/or more heavily loaded buses so that bus buffers do not need to be used" -- balbi