From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752580AbcGHG27 (ORCPT ); Fri, 8 Jul 2016 02:28:59 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:54666 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751299AbcGHG2w (ORCPT ); Fri, 8 Jul 2016 02:28:52 -0400 Date: Fri, 8 Jul 2016 08:28:46 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Tim Harvey Cc: Wolfram Sang , Fabio Estevam , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] i2c: imx: add retries for i2c-0 on Ventana boards Message-ID: <20160708062846.GI16643@pengutronix.de> References: <1467900229-5262-1-git-send-email-tharvey@gateworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1467900229-5262-1-git-send-email-tharvey@gateworks.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Tim, On Thu, Jul 07, 2016 at 07:03:49AM -0700, Tim Harvey wrote: > Gateworks Ventana IMX6 based boards have a Gateworks System Controller [1] > (gsc) device that can NAK i2c transactions when its busy in an ADC loop. As > this is always on i2c-0 we will add retries for that bus for any Ventana > board. The right thing is to fix the drivers IMHO. > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c > index 1844bc9..aec71c3 100644 > --- a/drivers/i2c/busses/i2c-imx.c > +++ b/drivers/i2c/busses/i2c-imx.c > @@ -460,6 +460,8 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx) > { > if (imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR) & I2SR_RXAK) { > dev_dbg(&i2c_imx->adapter.dev, "<%s> No ACK\n", __func__); > + if (i2c_imx->adapter.retries) > + return -EAGAIN; This is wrong, struct i2c_adapter::retries is for restarting a transfer on arbitration loss. > return -ENXIO; /* No ACK */ > } > > @@ -1068,6 +1070,16 @@ static int i2c_imx_probe(struct platform_device *pdev) > i2c_imx->adapter.dev.of_node = pdev->dev.of_node; > i2c_imx->base = base; > > + /* > + * The Gateworks Ventana has an i2c based system controller on i2c-0 > + * which emulates several standard i2c devices with existing drivers. > + * That device can NAK when its in an ADC loop. Add bus retries. > + */ > + if (of_machine_is_compatible("gw,ventana") && phy_addr == 0x021a0000) { Please don't. If you want to do handle a device in a special way, invent a device tree property, add it to your machine description and add handling here. Using of_machine_is_compatible + base address of the device to decide about configuration is a no go. > + dev_info(&pdev->dev, "Adding retries for Ventana GSC\n"); > + i2c_imx->adapter.retries = 3; > + } > + Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |