From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752043AbbBKIxp (ORCPT ); Wed, 11 Feb 2015 03:53:45 -0500 Received: from down.free-electrons.com ([37.187.137.238]:33702 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751782AbbBKIxn (ORCPT ); Wed, 11 Feb 2015 03:53:43 -0500 Date: Wed, 11 Feb 2015 09:53:39 +0100 From: Boris Brezillon To: Mark Rutland Cc: Thomas Gleixner , Jason Cooper , Nicolas Ferre , Jean-Christophe Plagniol-Villard , Alexandre Belloni , Rob Herring , Pawel Moll , Ian Campbell , Kumar Gala , "devicetree@vger.kernel.org" , "Rafael J. Wysocki" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v4 3/5] irqchip: Add DT binding doc for the virtual irq demuxer chip Message-ID: <20150211095339.0a2e4e7b@bbrezillon> In-Reply-To: <20150210204835.GL9432@leverpostej> References: <1422527620-8308-1-git-send-email-boris.brezillon@free-electrons.com> <1422527620-8308-4-git-send-email-boris.brezillon@free-electrons.com> <20150210153628.GF9432@leverpostej> <20150210165201.634bc04b@bbrezillon> <20150210204835.GL9432@leverpostej> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mark, On Tue, 10 Feb 2015 20:48:36 +0000 Mark Rutland wrote: > On Tue, Feb 10, 2015 at 03:52:01PM +0000, Boris Brezillon wrote: > > Hi Mark, > > > > On Tue, 10 Feb 2015 15:36:28 +0000 > > Mark Rutland wrote: > > > > > Hi Boris, > > > > > > On Thu, Jan 29, 2015 at 10:33:38AM +0000, Boris Brezillon wrote: > > > > Add documentation for the virtual irq demuxer. > > > > > > > > Signed-off-by: Boris Brezillon > > > > Acked-by: Nicolas Ferre > > > > --- > > > > .../bindings/interrupt-controller/dumb-demux.txt | 41 ++++++++++++++++++++++ > > > > 1 file changed, 41 insertions(+) > > > > create mode 100644 Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt > > > > > > > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt b/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt > > > > new file mode 100644 > > > > index 0000000..b9a7830 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/interrupt-controller/dumb-demux.txt > > > > @@ -0,0 +1,41 @@ > > > > +* Virtual Interrupt Demultiplexer > > > > + > > > > +This virtual demultiplexer simply forward all incoming interrupts to its > > > > +enabled/unmasked children. > > > > +It is only intended to be used by hardware that do not provide a proper way > > > > +to demultiplex a source interrupt, and thus have to wake all their children > > > > +up so that they can possibly handle the interrupt (if needed). > > > > +This can be seen as an alternative to shared interrupts when at least one > > > > +of the interrupt children is a timer (and require the irq to stay enabled > > > > +on suspend) while others are not. This will prevent calling irq handlers of > > > > +non timer devices while they are suspended. > > > > > > This sounds like a DT-workaround for a Linux implementation problem, and > > > I don't think this the right way to solve your problem. > > > > I understand your concern, but why are you answering while I asked for > > DT maintainers reviews for several days (if not several weeks). > > > > > > > > Why does this have to be in DT at all? Why can we not fix the core to > > > handle these details? > > > > We already discussed that with Rob and Thomas, and hiding such a > > demuxer chip is not an easy task. > > I'm open to any suggestion to do that, though I'd like you (I mean DT > > guys) to provide a working implementation (or at least a viable concept) > > that would silently demultiplex an irq. > > > > > > > > I am very much not keen on this binding. > > > > Yes, but do you have anything else to propose. > > We're experiencing this warning for 2 releases now, and this is time to > > find a solution (even if it's not a perfect one). > > Thoughts on the patch below? That's pretty much what I proposed in my first attempt to solve this problem [1] (except for a few things commented below). Anyway, Thomas suggested to go for the "dumb/virt irq demultiplexer" approach instead. > > Rather than handling this at the desc level it adds an extra flag to the > irqaction which can be set/unset during suspend for those irqs we don't > want to handle. That way we don't need to tell the core about the > mismatch explicitly in DT (or ACPI/board files/whatever). > > If we can request/free interrupts during suspend then there's some logic > missing, but it shows the basic idea. > > I didn't have a system to hand with shared mismatched IRQF_NO_SUSPEND > interrupts, so I had to fake that up in code for testing. > > Thanks, > Mark. > > ---->8---- > From f390ccbb31f06efee49b4469943c8d85d963bfb5 Mon Sep 17 00:00:00 2001 > From: Mark Rutland > Date: Tue, 10 Feb 2015 20:14:33 +0000 > Subject: [PATCH] genirq: allow mixed IRQF_NO_SUSPEND requests > > In some cases a physical IRQ line may be shared between devices from > which we expect interrupts during suspend (e.g. timers) and those we do > not (e.g. anything we cut the power to). Where a driver did not request > the interrupt with IRQF_NO_SUSPEND, it's unlikely that it can handle > being called during suspend, and it may bring down the system. > > This patch adds logic to automatically mark the irqactions for these > potentially unsafe handlers as disabled during suspend, leaving actions > with IRQF_NO_SUSPEND enabled. If an interrupt is raised on a shared line > during suspend, only the handlers requested with IRQF_NO_SUSPEND will be > called. The handlers requested without IRQF_NO_SUSPEND will be skipped > as if they had immediately returned IRQF_NONE. > > Cc: Boris Brezillon > Cc: Jason Cooper > Cc: Nicolas Ferre > Cc: Peter Zijlstra > Cc: Rafael J. Wysocki > Cc: Thomas Gleixner > Signed-off-by: Mark Rutland > --- > include/linux/interrupt.h | 4 ++++ > kernel/irq/handle.c | 13 +++++++++++- > kernel/irq/pm.c | 50 +++++++++++++++++++++++++++++++++++++++++++---- > 3 files changed, 62 insertions(+), 5 deletions(-) > > diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h > index d9b05b5..49dcb35 100644 > --- a/include/linux/interrupt.h > +++ b/include/linux/interrupt.h > @@ -57,6 +57,9 @@ > * IRQF_NO_THREAD - Interrupt cannot be threaded > * IRQF_EARLY_RESUME - Resume IRQ early during syscore instead of at device > * resume time. > + * IRQF_NO_ACTION - This irqaction should not be triggered. > + * Used during suspend for !IRQF_NO_SUSPEND irqactions which > + * share lines with IRQF_NO_SUSPEND irqactions. > */ > #define IRQF_DISABLED 0x00000020 > #define IRQF_SHARED 0x00000080 > @@ -70,6 +73,7 @@ > #define IRQF_FORCE_RESUME 0x00008000 > #define IRQF_NO_THREAD 0x00010000 > #define IRQF_EARLY_RESUME 0x00020000 > +#define IRQF_NO_ACTION 0x00040000 > > #define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD) > > diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c > index 6354802..44c8662 100644 > --- a/kernel/irq/handle.c > +++ b/kernel/irq/handle.c > @@ -130,6 +130,17 @@ void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action) > wake_up_process(action->thread); > } > > +static irqreturn_t __handle_irq_event_percpu(unsigned int irq, struct irqaction *action) > +{ > + /* > + * During suspend we must not call potentially unsafe irq handlers. > + * See suspend_suspendable_actions. > + */ > + if (unlikely(action->flags & IRQF_NO_ACTION)) > + return IRQ_NONE; Thomas was trying to avoid any new conditional code in the interrupt handling path, that's why I added a suspended_action list in my proposal. Even if your 'unlikely' statement make things better I'm pretty sure it adds some latency. > + return action->handler(irq, action->dev_id); > +} > + > irqreturn_t > handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action) > { > @@ -140,7 +151,7 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action) > irqreturn_t res; > > trace_irq_handler_entry(irq, action); > - res = action->handler(irq, action->dev_id); > + res = __handle_irq_event_percpu(irq, action); > trace_irq_handler_exit(irq, action, res); > > if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n", > diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c > index 3ca5325..9d8a71f 100644 > --- a/kernel/irq/pm.c > +++ b/kernel/irq/pm.c > @@ -43,9 +43,6 @@ void irq_pm_install_action(struct irq_desc *desc, struct irqaction *action) > > if (action->flags & IRQF_NO_SUSPEND) > desc->no_suspend_depth++; > - > - WARN_ON_ONCE(desc->no_suspend_depth && > - desc->no_suspend_depth != desc->nr_actions); Hm, actually this WARN_ON was here to detect offending drivers (those mixing handler with and without IRQF_NO_SUSPEND on a shared irq). IMO, removing it is not such a good idea. Best Regards, Boris [1]https://lkml.org/lkml/2014/12/15/551 -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com