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Date: Wed, 4 Mar 2015 20:00:40 +0000 From: Mark Rutland <mark.rutland@....com> To: "Rafael J. Wysocki" <rjw@...ysocki.net> Cc: Boris Brezillon <boris.brezillon@...e-electrons.com>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Jason Cooper <jason@...edaemon.net>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Nicolas Ferre <nicolas.ferre@...el.com>, Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>, Alexandre Belloni <alexandre.belloni@...e-electrons.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Linux PM list <linux-pm@...r.kernel.org> Subject: [PATCH] genirq: describe IRQF_COND_SUSPEND With certain restrictions it is possible for a wakeup device to share and IRQ with an IRQF_NO_SUSPEND user, and the warnings introduced by commit cab303be91dc47942bc25de33dc1140123540800 are spurious. The new IRQF_COND_SUSPEND flag allows drivers to tell the core when these restrictions are met, allowing spurious warnings to be silenced. This patch documents how IRQF_COND_SUSPEND is expected to be used, updating some of the text now made invalid by its addition. Signed-off-by: Mark Rutland <mark.rutland@....com> Cc: Boris Brezillon <boris.brezillon@...e-electrons.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com> --- Documentation/power/suspend-and-interrupts.txt | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) As promised previously, take IRQF_COND_SUSPEND into account in the documentation. Rafael, does this look OK to you? Thanks, Mark. diff --git a/Documentation/power/suspend-and-interrupts.txt b/Documentation/power/suspend-and-interrupts.txt index 50493c9..8afb29a 100644 --- a/Documentation/power/suspend-and-interrupts.txt +++ b/Documentation/power/suspend-and-interrupts.txt @@ -112,8 +112,9 @@ any special interrupt handling logic for it to work. IRQF_NO_SUSPEND and enable_irq_wake() ------------------------------------- -There are no valid reasons to use both enable_irq_wake() and the IRQF_NO_SUSPEND -flag on the same IRQ. +There are very few valid reasons to use both enable_irq_wake() and the +IRQF_NO_SUSPEND flag on the same IRQ, and it is never valid to use both for the +same device. First of all, if the IRQ is not shared, the rules for handling IRQF_NO_SUSPEND interrupts (interrupt handlers are invoked after suspend_device_irqs()) are @@ -122,4 +123,13 @@ handlers are not invoked after suspend_device_irqs()). Second, both enable_irq_wake() and IRQF_NO_SUSPEND apply to entire IRQs and not to individual interrupt handlers, so sharing an IRQ between a system wakeup -interrupt source and an IRQF_NO_SUSPEND interrupt source does not make sense. +interrupt source and an IRQF_NO_SUSPEND interrupt source does not generally +make sense. + +In rare cases an IRQ can be shared between a wakeup device driver and an +IRQF_NO_SUSPEND user. In order for this to be safe, the wakeup device driver +must be able to discern spurious IRQs from genuine wakeup events (signalling +the latter to the core with pm_system_wakeup()), must use enable_irq_wake() to +ensure that the IRQ will function as a wakeup source, and must request the IRQ +with IRQF_COND_SUSPEND to tell the core that it meets these requirements. If +these requirements are not met, it is not valid to use IRQF_COND_SUSPEND. -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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