From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756403AbaHHJgx (ORCPT ); Fri, 8 Aug 2014 05:36:53 -0400 Received: from mail-wi0-f175.google.com ([209.85.212.175]:41913 "EHLO mail-wi0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756361AbaHHJgv (ORCPT ); Fri, 8 Aug 2014 05:36:51 -0400 Date: Fri, 8 Aug 2014 11:37:01 +0200 From: Daniel Vetter To: Chris Wilson , Daniel Vetter , oscar.mateo@intel.com, intel-gfx@lists.freedesktop.org, Greg KH Cc: LKML Subject: Re: [Intel-gfx] [PATCH 45/53] drm/i915/bdw: Do not call intel_runtime_pm_get() in an interrupt Message-ID: <20140808093701.GO8727@phenom.ffwll.local> Mail-Followup-To: Chris Wilson , oscar.mateo@intel.com, intel-gfx@lists.freedesktop.org, Greg KH , LKML References: <1402673891-14618-1-git-send-email-oscar.mateo@intel.com> <1402673891-14618-46-git-send-email-oscar.mateo@intel.com> <20140618205413.GH5821@phenom.ffwll.local> <20140726102738.GA21056@nuc-i3427.alporthouse.com> <20140728085406.GX4747@phenom.ffwll.local> <20140729073748.GD21570@nuc-i3427.alporthouse.com> <20140729102636.GK4747@phenom.ffwll.local> <20140808092040.GD3021@nuc-i3427.alporthouse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140808092040.GD3021@nuc-i3427.alporthouse.com> X-Operating-System: Linux phenom 3.15.0-rc3+ 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, Aug 08, 2014 at 10:20:40AM +0100, Chris Wilson wrote: > On Tue, Jul 29, 2014 at 12:26:36PM +0200, Daniel Vetter wrote: > > On Tue, Jul 29, 2014 at 08:37:48AM +0100, Chris Wilson wrote: > > > On Mon, Jul 28, 2014 at 10:54:06AM +0200, Daniel Vetter wrote: > > > > On Sat, Jul 26, 2014 at 11:27:38AM +0100, Chris Wilson wrote: > > > > > On Wed, Jun 18, 2014 at 10:54:13PM +0200, Daniel Vetter wrote: > > > > > > On Fri, Jun 13, 2014 at 04:38:03PM +0100, oscar.mateo@intel.com wrote: > > > > > > > From: Oscar Mateo > > > > > > > > > > > > > > Or with a spinlock grabbed, because it might sleep, which is not > > > > > > > a nice thing to do. Instead, do the runtime_pm get/put together > > > > > > > with the create/destroy request, and handle the forcewake get/put > > > > > > > directly. > > > > > > > > > > > > > > Signed-off-by: Oscar Mateo > > > > > > > > > > > > Looks like a fixup that should be squashed into relevant earlier patches. > > > > > > > > > > The whole gen6_gt_force_wake_get() calling intel_runtime_pm_get() is > > > > > broken due to this - we must be able to read registers in atomic > > > > > context! > > > > > > > > > > Please revert c8c8fb33b37766acf6474784b0d5245dab9a1690 > > > > > > > > force_wake_get can't call runtime_pm_get becuase pm_get can sleep. So if > > > > you want to read registers from atomic context you have to have a runtime > > > > pm reference from someone else. > > > > > > Nope. That cannot work. > > > > Well it works currently. So where do you see the problem? > > Sampling registers from an timer - in particular, we really do not want > to disable runtime pm whilst trying to monitor the impact of runtime pm. In that case you can grab a runtime pm reference iff the device is powered on already. Which won't call anything scary, just amounts to an atomic_add_unless or so, and then drop it again. Unfortunately there doesn't seem to be such a thing around already, so need to add it first. Greg, how much would you freak out if we add something like /** * pm_runtime_get_unless_suspended - grab a rpm ref if the device is on * * Returns true if an rpm ref has been acquire, false otherwise. Can be * called from atomic context to e.g. sample perfomance counters (where we * obviously don't want to disturb system state if everything is off atm). */ static inline bool pm_runtime_get_unless_suspended(struct device *dev) { return atomic_add_unless(&dev->power.usage_count, 1, 0); } Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch