Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752695AbaFWWqa (ORCPT ); Mon, 23 Jun 2014 18:46:30 -0400 Received: from mail-vc0-f182.google.com ([209.85.220.182]:52737 "EHLO mail-vc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751437AbaFWWq1 (ORCPT ); Mon, 23 Jun 2014 18:46:27 -0400 MIME-Version: 1.0 In-Reply-To: <53A8AAC9.8030407@gmail.com> 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> <53A8AAC9.8030407@gmail.com> Date: Mon, 23 Jun 2014 15:46:26 -0700 X-Google-Sender-Auth: WhFsQTj3oDjhPx6SAnxgj4a0o6g Message-ID: Subject: Re: [PATCH] i2c: exynos5: Properly use the "noirq" variants of suspend/resume From: Doug Anderson To: Tomasz Figa Cc: Kevin Hilman , 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" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tomasz, On Mon, Jun 23, 2014 at 3:31 PM, Tomasz Figa wrote: > > > 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. ;) Wow, that would be seriously screwed up. OK, so to summarize my current plans: I won't spin this patch and we can see what Wolfram thinks. It may not be as beautiful as Kevin's suggestion to use Runtime PM but I also don't think it's insane. ...and I've got a request in to Samsung to use Runtime PM in the long run. If anyone at Samsung working on suspend/resume on exynos5420-pit or exynos5800-pi wants to add their Tested-by (or bug reports) I'm sure that would be appreciated. -Doug -- 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/