diff options
| -rw-r--r-- | Documentation/power/suspend-and-interrupts.txt | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/Documentation/power/suspend-and-interrupts.txt b/Documentation/power/suspend-and-interrupts.txt index 50493c9284b4..8afb29a8604a 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. |