Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753514AbaFWWcD (ORCPT ); Mon, 23 Jun 2014 18:32:03 -0400 Received: from mail-we0-f176.google.com ([74.125.82.176]:56012 "EHLO mail-we0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752968AbaFWWcA (ORCPT ); Mon, 23 Jun 2014 18:32:00 -0400 Message-ID: <53A8AAC9.8030407@gmail.com> Date: Tue, 24 Jun 2014 00:31:37 +0200 From: Tomasz Figa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Doug Anderson , Kevin Hilman CC: Wolfram Sang , Kukjin Kim , Javier Martinez Canillas , naveen krishna , Jingoo Han , Jean Delvare , Simon Glass , Paul Gortmaker , Masanari Iida , Sachin Kamat , "linux-i2c@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , linux-samsung-soc , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] i2c: exynos5: Properly use the "noirq" variants of suspend/resume References: <1403155273-1057-1-git-send-email-dianders@chromium.org> <7h8uosyc3k.fsf@paris.lan> <7hwqcbs166.fsf@paris.lan> <7h7g4brx6w.fsf@paris.lan> <53A4CADA.4030002@gmail.com> <7ha993p8v4.fsf@paris.lan> In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24.06.2014 00:27, Doug Anderson wrote: > Kevin, > > On Mon, Jun 23, 2014 at 3:19 PM, Kevin Hilman wrote: >> Doug Anderson writes: >> >> [...] >> >>> On Fri, Jun 20, 2014 at 4:59 PM, Tomasz Figa wrote: >>>> >>>> I'm not sure noirq is going to work correctly, at least not with current >>>> callbacks. I can see a call to clk_prepare_enable() there which needs to >>>> acquire a mutex. >>> >>> Nice catch, thanks! :) >>> >>> OK, looking at that now. Interestingly this doesn't seem to cause us >>> problems in our ChromeOS 3.8 tree. I just tried enabling: >>> CONFIG_DEBUG_ATOMIC_SLEEP=y >>> >>> ...and confirmed that I got it on right: >>> >>> # zgrep -i atomic /proc/config.gz >>> CONFIG_DEBUG_ATOMIC_SLEEP=y >>> >>> I can suspend/resume with no problems. My bet is that it works fine because: >>> >>> * resume_noirq is not considered "atomic" in the sense enforced by >>> CONFIG_DEBUG_ATOMIC_SLEEP (at least not in 3.8--I haven't tried on >>> ToT) >> >> The reason is because "noirq" in the suspend/resume path actually means >> no *device* IRQs for that specific device. >> >> It's often assumed that the "noirq" callbacks are called with *all* >> interrupts disabled, but that's not the case. Only the IRQs for that >> specific device are disabled when its noirq callbacks run. > > Ah, so even with my fix of moving to noirq we could still be broken if > the system decided to enable interrupts for the device before the i2c > controller get resumed then we'd still be SOL. > > ...oh, but if it matches probe order then maybe we're guaranteed for > that not to happen? We know that we will probe the i2c bus before the > devices on it, right? If the mentioned device is a child of the I2C controller then the parent-child relation determines the order. Otherwise (e.g. another, non-I2C interrupt source that just triggers some operation on an I2C device like voltage regulator) we're doomed. ;) Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/