From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ray Jui Subject: Re: [PATCH v4 2/3] i2c: iproc: Add Broadcom iProc I2C Driver Date: Sat, 17 Jan 2015 13:26:41 -0800 Message-ID: <54BAD391.9080909@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> <20150117211017.GD22880@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20150117211017.GD22880-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: =?windows-1252?Q?Uwe_Kleine-K=F6nig?= 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: devicetree@vger.kernel.org On 1/17/2015 1:10 PM, Uwe Kleine-K=F6nig wrote: > Hello, >=20 > 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, >>> >>> 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. >>> >> Yes. No theoretical upper limit in the case when clock is stretched = by >> the slave. But how would adding an additional interrupt completion c= heck >> below help? I assume you want the the check to be like the following= ? >> >> time_left =3D wait_for_completion_timeout(&iproc_i2c->done, time_le= ft); >> >> /* 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 =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: >=20 > time_left =3D wait_for_completion_timeout(&iproc_i2c->done, time_lef= t); >=20 > if (!transfer_was_complete) { > handle_error(); > ... >=20 > } >=20 > handle_successful_transfer(); >=20 > and time_left =3D=3D 0 is not a reliable indicator that the transfer = failed. >=20 > Best regards > Uwe >=20 Okay I'll check both time_left and transfer_was_done: time_left =3D wait_for_completion_timeout(&iproc_i2c->done, time_left)= ; /* disable all interrupts */ writel(0, iproc_i2c->base + IE_OFFSET); if (!time_left && !atomic_read(&iproc_i2c->transfer_is_successful)) { dev_err(iproc_i2c->device, "transaction timed out\n"); /* 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; } -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html