From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nishanth Menon Subject: [Fwd: Re: [PATCH] i2c: omap: highspeed only over 1000mhz] Date: Mon, 20 Oct 2008 08:27:50 -0500 Message-ID: <48FC8756.8060807@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from an-out-0708.google.com ([209.85.132.245]:9872 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751673AbYJTN1y (ORCPT ); Mon, 20 Oct 2008 09:27:54 -0400 Received: by an-out-0708.google.com with SMTP id d40so87021and.103 for ; Mon, 20 Oct 2008 06:27:53 -0700 (PDT) Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Dist- Linux-OMAP-vger , felipe.balbi@nokia.com Looping in list. my html mail bounced :( -------- Original Message -------- Subject: Re: [PATCH] i2c: omap: highspeed only over 1000mhz Date: Mon, 20 Oct 2008 08:18:20 -0500 =46rom: Nishanth Menon To: felipe.balbi@nokia.com CC: linux-omap@vger.kernel.org, Ben Dooks , Tony Lindgren References: <1224277795-17143-1-git-send-email-felipe.balbi@nokia.com> <20081020102659.GA31599@gandalf.research.nokia.com> <48FC7CA9.4040102@gmail.com> <20081020125355.GC31599@gandalf.research.nokia.com> =46elipe Balbi said the following on 10/20/2008 07:53 AM: > On Mon, Oct 20, 2008 at 07:42:17AM -0500, ext Nishanth Menon wrote: > =20 >> Felipe, >> Felipe Balbi said the following on 10/20/2008 05:26 AM: >> =20 >>> 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 *d= ev) >>> psc =3D psc - 1; >>> =20 >>> /* If configured for High Speed */ >>> - if (dev->speed > 400) { >>> + if (dev->speed > 1000) { >>> =20 >>> =20 >> Ref: http://www.nxp.com/acrobat_download/literature/9398/39340011.pd= f >> 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? >> =20 > > http://www.standardics.nxp.com/support/documents/i2c/pdf/i2c.bus.spec= ification.pdf > > section 5.2: > > "Fast-mode Plus (Fm+) devices offer an increase in I2C-bus transfer s= peeds 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 protoc= ol and data > format is maintained as with the Fast- or Standard-mode system. Fm+ d= evices 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 ne= ed > to be used" > > =20 Aaah, rev 3 of the spec! However, OMAP TRM says: " three multimaster HS I2C controllers have the following features: =E2=80=A2 Compliance with Philips I2C specification version 2.1 " So does this change make sense? FM+ devices might actually be confusing the OMAP3430? Regards, Nishanth Menon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html