From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH] i2c: i2c_mxs: Set ACK_MODE bit Date: Tue, 20 Aug 2013 20:52:27 +0200 Message-ID: <20130820185227.GO30496@pengutronix.de> References: <1372780860-12972-1-git-send-email-fabio.estevam@freescale.com> <20130815100809.GE2987@katana> <52120D35.707@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <52120D35.707-KZfg59tc24xl57MIdRCFDg@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Fabio Estevam Cc: Wolfram Sang , marex-ynQEQJNshbs@public.gmane.org, shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, festevam-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, alexandre.belloni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org, cb-/RsSufbtIHM@public.gmane.org List-Id: linux-i2c@vger.kernel.org Hello, On Mon, Aug 19, 2013 at 09:19:01AM -0300, Fabio Estevam wrote: > On 08/15/2013 07:08 AM, Wolfram Sang wrote: > >On Tue, Jul 02, 2013 at 01:01:00PM -0300, Fabio Estevam wrote: > >>According to mx23 erratum 2727: > >> > >>"2727 : I2C 9th Clock Pulse (ACK) not generated when RETAIN_CLOCK s= et. > >> > >>Description: > >> > >>When RETAIN_CLOCK is set, the ninth clock pulse (ACK) is not genera= ted. > >>However, the SDA line is read at the proper timing interval. If > >>RETAIN_CLOCK is cleared, the ninth clock pulse is generated. > >>Also, the HW_I2C_VERSION register incorrectly states the version is= 1.2. > >>It should be 1.3. > >> > >>Workaround: > >>HW_I2C_CTRL1[ACK_MODE] has default value of 0. It should be set to = 1 to > >>enable the fix for this issue." > >> > >>It has also been noticed that mx28 needs to implement this fix in o= rder to have > >>SMBus to work properly. > >> > >>Reported-by: Christoph Baumann > >>Signed-off-by: Fabio Estevam > > > >What's with this one? Bogus? Needed? Still needed after PIO rework? >=20 > According to the mx23 erratum 2727 this patch is needed. Last time I worked with i2c stuff on mxs my impression was the mx23 erratum 2727 is non-sense. Having HW_I2C_CTRL1[ACK_MODE] set or not didn't made any difference in my tests. I suspect that the description isn't complete. So the driver does already use RETAIN_CLOCK (for the select phase) which up to know didn't made any problems on mx23 even without having ACK_MODE=3D1. The statement about the HW_I2C_VERSION register appears just misplaced there. So I'd vote for not taking this patch until there is a better understanding of the eventual problem. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= |