From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH] i2c: rk3x: Increase wait timeout to 1 second Date: Mon, 4 May 2015 10:33:12 +0200 Message-ID: <20150504083312.GN25193@pengutronix.de> References: <1430430247-9632-1-git-send-email-dianders@chromium.org> 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: <1430430247-9632-1-git-send-email-dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Doug Anderson Cc: Wolfram Sang , Addy Ke , Max Schwarz , Heiko Stuebner , Dmitry Torokhov , linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org On Thu, Apr 30, 2015 at 02:44:07PM -0700, Doug Anderson wrote: > While it's not sensible for an i2c command to _actually_ need more > than 200ms to complete, let's increase the timeout anyway. Why? It > turns out that if you've got a large number of printks going out to a > serial console, interrupts on a CPU can be disabled for hundreds of > milliseconds. That's not a great situation to be in to start with > (maybe we should put a cap in vprintk_emit()) but it's pretty annoyin= g > to start seeing unexplained i2c timeouts. >=20 > A normal system shouldn't see i2c timeouts anyway, so increasing the > timeout should help people debugging without hurting other people > excessively. Hmm, correct me if I'm wrong: You say that the following can happen: rk3x_i2c_xfer calls wait_event_timeout and blocks schedule ... disable_irqs ... xfer complete ... do some work ... enabl= e_irqs control back to i2c driver after timeout elapsed wait_event_timeout returned 0 The documentation of wait_event_timeout tells: * Returns: * 0 if the @condition evaluated to %false after the @timeout elapsed, * 1 if the @condition evaluated to %true after the @timeout elapsed, * or the remaining jiffies (at least 1) if the @condition evaluated * to %true before the @timeout elapsed. Where is the misunderstanding? Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.de/= |