From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 45/53] drm/i915/bdw: Do not call intel_runtime_pm_get() in an interrupt Date: Fri, 8 Aug 2014 11:37:01 +0200 Message-ID: <20140808093701.GO8727@phenom.ffwll.local> 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-Transfer-Encoding: 7bit Return-path: Received: from mail-we0-f169.google.com (mail-we0-f169.google.com [74.125.82.169]) by gabe.freedesktop.org (Postfix) with ESMTP id CDDD76E06D for ; Fri, 8 Aug 2014 02:36:50 -0700 (PDT) Received: by mail-we0-f169.google.com with SMTP id u56so5364087wes.28 for ; Fri, 08 Aug 2014 02:36:49 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20140808092040.GD3021@nuc-i3427.alporthouse.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Chris Wilson , Daniel Vetter , oscar.mateo@intel.com, intel-gfx@lists.freedesktop.org, Greg KH Cc: LKML List-Id: intel-gfx@lists.freedesktop.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