From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752469AbaKGM24 (ORCPT ); Fri, 7 Nov 2014 07:28:56 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:48327 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752380AbaKGM2x (ORCPT ); Fri, 7 Nov 2014 07:28:53 -0500 Date: Fri, 7 Nov 2014 13:28:51 +0100 From: Pavel Machek To: Krzysztof Kozlowski Cc: "Rafael J. Wysocki" , Len Brown , Jonathan Corbet , Russell King , Dan Williams , Vinod Koul , Ulf Hansson , Alan Stern , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, Lars-Peter Clausen , Michal Simek , Kevin Hilman , Laurent Pinchart , Kyungmin Park , Marek Szyprowski , Bartlomiej Zolnierkiewicz Subject: Re: [PATCH v9 2/4] amba: Don't unprepare the clocks if device driver wants IRQ safe runtime PM Message-ID: <20141107122850.GB20419@amd> References: <1415105570-7871-1-git-send-email-k.kozlowski@samsung.com> <1415105570-7871-3-git-send-email-k.kozlowski@samsung.com> <20141104201834.GC15071@amd> <1415176978.15850.11.camel@AMDC1943> <20141107121320.GA20419@amd> <1415362683.31102.6.camel@AMDC1943> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1415362683.31102.6.camel@AMDC1943> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 2014-11-07 13:18:03, Krzysztof Kozlowski wrote: > On pią, 2014-11-07 at 13:13 +0100, Pavel Machek wrote: > > On Wed 2014-11-05 09:42:58, Krzysztof Kozlowski wrote: > > > On wto, 2014-11-04 at 21:18 +0100, Pavel Machek wrote: > > > > On Tue 2014-11-04 13:52:48, Krzysztof Kozlowski wrote: > > > > > The AMBA bus driver defines runtime Power Management functions which > > > > > disable and unprepare AMBA bus clock. This is problematic for runtime PM > > > > > because unpreparing a clock might sleep so it is not interrupt safe. > > > > > > > > > > However some drivers may want to implement runtime PM functions in > > > > > interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA > > > > > bus driver should only disable/enable the clock in runtime suspend and > > > > > resume callbacks. > > > > > > > > > > > > > > > > > /* > > > > > * Hooks to provide runtime PM of the pclk (bus clock). It is safe to > > > > > * enable/disable the bus clock at runtime PM suspend/resume as this > > > > > @@ -95,8 +102,14 @@ static int amba_pm_runtime_suspend(struct device *dev) > > > > > struct amba_device *pcdev = to_amba_device(dev); > > > > > int ret = pm_generic_runtime_suspend(dev); > > > > > > > > > > - if (ret == 0 && dev->driver) > > > > > - clk_disable_unprepare(pcdev->pclk); > > > > > + if (ret == 0 && dev->driver) { > > > > > + pcdev->irq_safe = get_pm_runtime_irq_safe(dev); > > > > > + > > > > > + if (pcdev->irq_safe) > > > > > + clk_disable(pcdev->pclk); > > > > > + else > > > > > + clk_disable_unprepare(pcdev->pclk); > > > > > + } > > > > > > > > So you can handle the case of !pcdev->irq_safe. What is the penalty > > > > for always assuming !pcdev->irq_safe? > > > > > > The penalty (for pl330 driver) would be that the runtime resume/suspend > > > cannot happen from atomic context > > > => pm_runtime_get_sync() cannot be called from atomic context > > > => complete rework of runtime PM for pl330 DMA driver because now > > > one of pm_runtime_get_sync() calls is in device_issue_pending > > > callback which may not sleep. And by "rework" I also mean that > > > I do not know how to do this... yet. > > > > I still don't get it. You say that you don't know how to handle > > !pcdev->irq_safe case... Yet have code above that tries to handle it. > > > > If that case can't be sanely handled, I'd expect > > BUG_ON(!pcdev->irq_safe). > > Hmmm... I could misunderstand your question. The amba/bus.c driver can > handle both cases. However this varies for child drivers (which use > these runtime PM callbacks too). For pl330 cannot handle non-irq-safe. > Other drivers can. Ok, so pl330 can't handle non-irq-safe callbacks. What about the other solution preserving consistency -- can we make sure all callbacks are irq-safe with acceptable penalty? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html