From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH v4 2/3] i2c: iproc: Add Broadcom iProc I2C Driver Date: Sat, 17 Jan 2015 22:10:17 +0100 Message-ID: <20150117211017.GD22880@pengutronix.de> References: <1421274213-3544-1-git-send-email-rjui@broadcom.com> <1421274213-3544-3-git-send-email-rjui@broadcom.com> <20150115084119.GN22880@pengutronix.de> <54B98C18.4080807@broadcom.com> <20150117160113.GA22880@pengutronix.de> <54BABEE9.8070801@broadcom.com> <20150117201849.GC22880@pengutronix.de> <54BACB66.6040909@broadcom.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: <54BACB66.6040909-dY08KVG/lbpWk0Htik3J/w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ray Jui Cc: Wolfram Sang , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Grant Likely , Christian Daudt , Matt Porter , Florian Fainelli , Russell King , Scott Branden , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, bcm-kernel-feedback-list-dY08KVG/lbpWk0Htik3J/w@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org Hello, On Sat, Jan 17, 2015 at 12:51:50PM -0800, Ray Jui wrote: > On 1/17/2015 12:18 PM, Uwe Kleine-K=F6nig wrote: > > Hello, > >=20 > > On Sat, Jan 17, 2015 at 11:58:33AM -0800, Ray Jui wrote: > >> On 1/17/2015 8:01 AM, Uwe Kleine-K=F6nig wrote: > >>> On Fri, Jan 16, 2015 at 02:09:28PM -0800, Ray Jui wrote: > >>>> On 1/15/2015 12:41 AM, Uwe Kleine-K=F6nig wrote: > >>>>> On Wed, Jan 14, 2015 at 02:23:32PM -0800, Ray Jui wrote: > >>>>>> + */ > >>>>>> + val =3D 1 << M_CMD_START_BUSY_SHIFT; > >>>>>> + if (msg->flags & I2C_M_RD) { > >>>>>> + val |=3D (M_CMD_PROTOCOL_BLK_RD << M_CMD_PROTOCOL_SHIFT) | > >>>>>> + (msg->len << M_CMD_RD_CNT_SHIFT); > >>>>>> + } else { > >>>>>> + val |=3D (M_CMD_PROTOCOL_BLK_WR << M_CMD_PROTOCOL_SHIFT); > >>>>>> + } > >>>>>> + writel(val, iproc_i2c->base + M_CMD_OFFSET); > >>>>>> + > >>>>>> + time_left =3D wait_for_completion_timeout(&iproc_i2c->done, = time_left); > >>>>> > >>>>> When the interrupt fires here after the complete timed out and = before > >>>>> you disable the irq you still throw the result away. > >>>> Yes, but then this comes down to the fact that if it has reached= the > >>>> point that is determined to be a timeout condition in the driver= , one > >>>> should really treat it as timeout error. In a normal condition, > >>>> time_left should never reach zero. > >>> I don't agree here. I'm not sure there is a real technical reason= , > >>> though. But still if you're in a "success after timeout already o= ver" > >>> situation it's IMHO better to interpret it as success, not timeou= t. > >>> > >> The thing is, the interrupt should never fire after > >> wait_for_completion_timeout returns zero here. If it does, then th= e > >> issue is really that the timeout value set in the driver is probab= ly not > >> long enough. I just checked other I2C drivers. I think the way how > >> timeout is handled here is consistent with other I2C drivers. > > In the presence of Clock stretching there is no (theorethical) uppe= r > > limit for the time needed to transfer a given message, is there? So > > (theoretically) you can never be sure not to interrupt an ongoing > > transfer. > >=20 > Yes. No theoretical upper limit in the case when clock is stretched b= y > the slave. But how would adding an additional interrupt completion ch= eck > below help? I assume you want the the check to be like the following? >=20 > time_left =3D wait_for_completion_timeout(&iproc_i2c->done, time_lef= t); >=20 > /* disable all interrupts */ > writel(0, iproc_i2c->base + IE_OFFSET); >=20 > if (!time_left && !completion_done()) { > dev_err(iproc_i2c->device, "transaction timed out\n"); >=20 > /* flush FIFOs */ > val =3D (1 << M_FIFO_RX_FLUSH_SHIFT) | > (1 << M_FIFO_TX_FLUSH_SHIFT); > writel(val, iproc_i2c->base + M_FIFO_CTRL_OFFSET); > return -ETIMEDOUT; > } No, I want: time_left =3D wait_for_completion_timeout(&iproc_i2c->done, time_left)= ; if (!transfer_was_complete) { handle_error(); ... } handle_successful_transfer(); and time_left =3D=3D 0 is not a reliable indicator that the transfer fa= iled. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= | From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Sat, 17 Jan 2015 22:10:17 +0100 Subject: [PATCH v4 2/3] i2c: iproc: Add Broadcom iProc I2C Driver In-Reply-To: <54BACB66.6040909@broadcom.com> References: <1421274213-3544-1-git-send-email-rjui@broadcom.com> <1421274213-3544-3-git-send-email-rjui@broadcom.com> <20150115084119.GN22880@pengutronix.de> <54B98C18.4080807@broadcom.com> <20150117160113.GA22880@pengutronix.de> <54BABEE9.8070801@broadcom.com> <20150117201849.GC22880@pengutronix.de> <54BACB66.6040909@broadcom.com> Message-ID: <20150117211017.GD22880@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello, On Sat, Jan 17, 2015 at 12:51:50PM -0800, Ray Jui wrote: > On 1/17/2015 12:18 PM, Uwe Kleine-K?nig wrote: > > Hello, > > > > On Sat, Jan 17, 2015 at 11:58:33AM -0800, Ray Jui wrote: > >> On 1/17/2015 8:01 AM, Uwe Kleine-K?nig wrote: > >>> On Fri, Jan 16, 2015 at 02:09:28PM -0800, Ray Jui wrote: > >>>> On 1/15/2015 12:41 AM, Uwe Kleine-K?nig wrote: > >>>>> On Wed, Jan 14, 2015 at 02:23:32PM -0800, Ray Jui wrote: > >>>>>> + */ > >>>>>> + val = 1 << M_CMD_START_BUSY_SHIFT; > >>>>>> + if (msg->flags & I2C_M_RD) { > >>>>>> + val |= (M_CMD_PROTOCOL_BLK_RD << M_CMD_PROTOCOL_SHIFT) | > >>>>>> + (msg->len << M_CMD_RD_CNT_SHIFT); > >>>>>> + } else { > >>>>>> + val |= (M_CMD_PROTOCOL_BLK_WR << M_CMD_PROTOCOL_SHIFT); > >>>>>> + } > >>>>>> + writel(val, iproc_i2c->base + M_CMD_OFFSET); > >>>>>> + > >>>>>> + time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left); > >>>>> > >>>>> When the interrupt fires here after the complete timed out and before > >>>>> you disable the irq you still throw the result away. > >>>> Yes, but then this comes down to the fact that if it has reached the > >>>> point that is determined to be a timeout condition in the driver, one > >>>> should really treat it as timeout error. In a normal condition, > >>>> time_left should never reach zero. > >>> I don't agree here. I'm not sure there is a real technical reason, > >>> though. But still if you're in a "success after timeout already over" > >>> situation it's IMHO better to interpret it as success, not timeout. > >>> > >> The thing is, the interrupt should never fire after > >> wait_for_completion_timeout returns zero here. If it does, then the > >> issue is really that the timeout value set in the driver is probably not > >> long enough. I just checked other I2C drivers. I think the way how > >> timeout is handled here is consistent with other I2C drivers. > > In the presence of Clock stretching there is no (theorethical) upper > > limit for the time needed to transfer a given message, is there? So > > (theoretically) you can never be sure not to interrupt an ongoing > > transfer. > > > Yes. No theoretical upper limit in the case when clock is stretched by > the slave. But how would adding an additional interrupt completion check > below help? I assume you want the the check to be like the following? > > time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left); > > /* disable all interrupts */ > writel(0, iproc_i2c->base + IE_OFFSET); > > if (!time_left && !completion_done()) { > dev_err(iproc_i2c->device, "transaction timed out\n"); > > /* flush FIFOs */ > val = (1 << M_FIFO_RX_FLUSH_SHIFT) | > (1 << M_FIFO_TX_FLUSH_SHIFT); > writel(val, iproc_i2c->base + M_FIFO_CTRL_OFFSET); > return -ETIMEDOUT; > } No, I want: time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left); if (!transfer_was_complete) { handle_error(); ... } handle_successful_transfer(); and time_left == 0 is not a reliable indicator that the transfer failed. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ | From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752382AbbAQVKn (ORCPT ); Sat, 17 Jan 2015 16:10:43 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:50512 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752112AbbAQVKl (ORCPT ); Sat, 17 Jan 2015 16:10:41 -0500 Date: Sat, 17 Jan 2015 22:10:17 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Ray Jui Cc: Wolfram Sang , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Grant Likely , Christian Daudt , Matt Porter , Florian Fainelli , Russell King , Scott Branden , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com, devicetree@vger.kernel.org Subject: Re: [PATCH v4 2/3] i2c: iproc: Add Broadcom iProc I2C Driver Message-ID: <20150117211017.GD22880@pengutronix.de> References: <1421274213-3544-1-git-send-email-rjui@broadcom.com> <1421274213-3544-3-git-send-email-rjui@broadcom.com> <20150115084119.GN22880@pengutronix.de> <54B98C18.4080807@broadcom.com> <20150117160113.GA22880@pengutronix.de> <54BABEE9.8070801@broadcom.com> <20150117201849.GC22880@pengutronix.de> <54BACB66.6040909@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <54BACB66.6040909@broadcom.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 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, On Sat, Jan 17, 2015 at 12:51:50PM -0800, Ray Jui wrote: > On 1/17/2015 12:18 PM, Uwe Kleine-König wrote: > > Hello, > > > > On Sat, Jan 17, 2015 at 11:58:33AM -0800, Ray Jui wrote: > >> On 1/17/2015 8:01 AM, Uwe Kleine-König wrote: > >>> On Fri, Jan 16, 2015 at 02:09:28PM -0800, Ray Jui wrote: > >>>> On 1/15/2015 12:41 AM, Uwe Kleine-König wrote: > >>>>> On Wed, Jan 14, 2015 at 02:23:32PM -0800, Ray Jui wrote: > >>>>>> + */ > >>>>>> + val = 1 << M_CMD_START_BUSY_SHIFT; > >>>>>> + if (msg->flags & I2C_M_RD) { > >>>>>> + val |= (M_CMD_PROTOCOL_BLK_RD << M_CMD_PROTOCOL_SHIFT) | > >>>>>> + (msg->len << M_CMD_RD_CNT_SHIFT); > >>>>>> + } else { > >>>>>> + val |= (M_CMD_PROTOCOL_BLK_WR << M_CMD_PROTOCOL_SHIFT); > >>>>>> + } > >>>>>> + writel(val, iproc_i2c->base + M_CMD_OFFSET); > >>>>>> + > >>>>>> + time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left); > >>>>> > >>>>> When the interrupt fires here after the complete timed out and before > >>>>> you disable the irq you still throw the result away. > >>>> Yes, but then this comes down to the fact that if it has reached the > >>>> point that is determined to be a timeout condition in the driver, one > >>>> should really treat it as timeout error. In a normal condition, > >>>> time_left should never reach zero. > >>> I don't agree here. I'm not sure there is a real technical reason, > >>> though. But still if you're in a "success after timeout already over" > >>> situation it's IMHO better to interpret it as success, not timeout. > >>> > >> The thing is, the interrupt should never fire after > >> wait_for_completion_timeout returns zero here. If it does, then the > >> issue is really that the timeout value set in the driver is probably not > >> long enough. I just checked other I2C drivers. I think the way how > >> timeout is handled here is consistent with other I2C drivers. > > In the presence of Clock stretching there is no (theorethical) upper > > limit for the time needed to transfer a given message, is there? So > > (theoretically) you can never be sure not to interrupt an ongoing > > transfer. > > > Yes. No theoretical upper limit in the case when clock is stretched by > the slave. But how would adding an additional interrupt completion check > below help? I assume you want the the check to be like the following? > > time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left); > > /* disable all interrupts */ > writel(0, iproc_i2c->base + IE_OFFSET); > > if (!time_left && !completion_done()) { > dev_err(iproc_i2c->device, "transaction timed out\n"); > > /* flush FIFOs */ > val = (1 << M_FIFO_RX_FLUSH_SHIFT) | > (1 << M_FIFO_TX_FLUSH_SHIFT); > writel(val, iproc_i2c->base + M_FIFO_CTRL_OFFSET); > return -ETIMEDOUT; > } No, I want: time_left = wait_for_completion_timeout(&iproc_i2c->done, time_left); if (!transfer_was_complete) { handle_error(); ... } handle_successful_transfer(); and time_left == 0 is not a reliable indicator that the transfer failed. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |