From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [2/5] i2c: davinci: query STP always when NACK is received Date: Fri, 21 Nov 2014 14:10:08 +0100 Message-ID: <20141121131008.GQ27002@pengutronix.de> References: <1416477788-5544-3-git-send-email-grygorii.strashko@ti.com> <20141120221953.GI27002@pengutronix.de> <546F34B9.1000206@ti.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: <546F34B9.1000206-l0cyMroinI0@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Grygorii Strashko Cc: Wolfram Sang , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Sekhar Nori , Kevin Hilman , Santosh Shilimkar , Murali Karicheri List-Id: linux-i2c@vger.kernel.org Hello, On Fri, Nov 21, 2014 at 02:48:57PM +0200, Grygorii Strashko wrote: > On 11/21/2014 12:19 AM, Uwe Kleine-K=F6nig wrote: > >> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses= /i2c-davinci.c > >> index 9bbfb8f..2cef115 100644 > >> --- a/drivers/i2c/busses/i2c-davinci.c > >> +++ b/drivers/i2c/busses/i2c-davinci.c > >> @@ -411,11 +411,9 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap= , struct i2c_msg *msg, int stop) > >> if (dev->cmd_err & DAVINCI_I2C_STR_NACK) { > >> if (msg->flags & I2C_M_IGNORE_NAK) > >> return msg->len; > >> - if (stop) { > >> - w =3D davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); > >> - w |=3D DAVINCI_I2C_MDR_STP; > >> - davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w); > >> - } > >> + w =3D davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); > >> + w |=3D DAVINCI_I2C_MDR_STP; > >> + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w); > > I think this is a good change, but I wonder if the handling of > > I2C_M_IGNORE_NAK is correct here. If the controller reports a NACK = say > > for the 2nd byte of a 5-byte-message, the transfer supposed to > > continue, right? (Hmm, maybe the framework handle this and restarts= the > > transfer with I2C_M_NOSTART but the davinci driver doesn't seem to > > handle this flag?) >=20 > Have nothing to say about handling of I2C_M_IGNORE_NAK. I'm not going= to > change current behavior - davinci driver will interrupt transfer of i= 2c_msg always > in case of NACK and start transfer of the next i2c_msg (if exist). > In my opinion, Above question is out of scope of this patch. Yeah right, that's exactly what I thought. Thinking again I wonder if with your change handling is correct when th= e sender wants to do a repeated start. That would need a more detailed look into the driver. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= |