From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Zhao Subject: Re: [PATCH 1/4] i2c: imx: check busy bit when START/STOP Date: Fri, 2 Oct 2009 16:17:09 +0800 Message-ID: <4e090d470910020117w620fda4cta7b26b912d01bc24@mail.gmail.com> References: <1254359613-21210-1-git-send-email-linuxzsc@gmail.com> <4e090d470910010103o611d9fb2t3acf93632216fc88@mail.gmail.com> <20091001083831.GD27039@pengutronix.de> <4e090d470910010211k4ce78763i1a5163ec6ea57fe8@mail.gmail.com> <20091001095239.GE27039@pengutronix.de> <4e090d470910010754r1ebc4455u6220ccfd803491b0@mail.gmail.com> <20091001163753.GA20103@pengutronix.de> <4e090d470910011757g261c693ehdca40ce43ebee2ec@mail.gmail.com> <20091002072643.GH27039@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20091002072643.GH27039-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sascha Hauer Cc: Wolfram Sang , kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-i2c@vger.kernel.org On Fri, Oct 2, 2009 at 3:26 PM, Sascha Hauer w= rote: > On Fri, Oct 02, 2009 at 08:57:04AM +0800, Richard Zhao wrote: >> On Fri, Oct 2, 2009 at 12:37 AM, Wolfram Sang wrote: >> >> > Ah, so 'make the driver work on i.MX51' is a good statement whi= ch should >> >> > be part of the commit message. >> >> Well, maybe I can mention it. >> >> But I think the good point is to present what you modified, not t= he side effect. >> > >> > It is not the side effect but the intention :) As no code is chang= ed without a >> > need, the reason really should be in the patch description. >> No, it's not intention. I'm just trying to make the controller work = in >> a right way. Without this patch, maybe some other fast cpus have >> problem too. I just tested mx31 and mx51. I will add "Without this >> patch, i2c on some fast SoCs (for example imx51) will not work". Is = it >> ok for you? > > Please remember that we do not have i.MX51 support in mainline, so th= is > is irrelevant atm. So I don't need to meantion mx51? "Without this patch, i2c on some fast SoCs will not work" is all right? > >> > >> >> Yes. But I don't have multi-master system. So I can't say that. >> >> The code is just taken from Freescale latest code. Without it, It >> >> could also cause a device error. I forget the details. =A0Anyway,= it >> >> doesn't make anything wrong. >> > >> > Do you know where the details are explained? >> No, I don't. I don't have device in hand now. If you have, could you >> please help do a simple test? >> Use hw to simulate multi-master system. Before execute xfer, you fir= st >> pull down SDA, then pull down SDC. It simulates a START. and execute >> xfer to see whether IBB is set? > > No, we won't do any tests on hardware. > > At the moment we have a driver which is not multi master capable. > Looking at the datasheet the change you do seems not enough to change > this. So we should take a patch which changes something from which yo= u > think it might be needed? And you don't even have the details at hand= ? > > No. Ok, It seems I have no reason to keep the busy wait before START. Wolfram, do you agree to remove the busy wait? I saw you submmited the original driver. Let get away from multi-master. There's nearly no multi-master i2c bus system in reality. Thanks Richard > > Sascha > > -- > Pengutronix e.K. =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = | =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > Industrial Linux Solutions =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | http://w= ww.pengutronix.de/ =A0| > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0= =A0 =A0| > Amtsgericht Hildesheim, HRA 2686 =A0 =A0 =A0 =A0 =A0 | Fax: =A0 +49-5= 121-206917-5555 | >