diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/power/suspend-and-interrupts.txt | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/Documentation/power/suspend-and-interrupts.txt b/Documentation/power/suspend-and-interrupts.txt index 2f9c5a5fcb25..8afb29a8604a 100644 --- a/Documentation/power/suspend-and-interrupts.txt +++ b/Documentation/power/suspend-and-interrupts.txt @@ -40,8 +40,10 @@ but also to IPIs and to some other special-purpose interrupts. The IRQF_NO_SUSPEND flag is used to indicate that to the IRQ subsystem when requesting a special-purpose interrupt. It causes suspend_device_irqs() to -leave the corresponding IRQ enabled so as to allow the interrupt to work all -the time as expected. +leave the corresponding IRQ enabled so as to allow the interrupt to work as +expected during the suspend-resume cycle, but does not guarantee that the +interrupt will wake the system from a suspended state -- for such cases it is +necessary to use enable_irq_wake(). Note that the IRQF_NO_SUSPEND flag affects the entire IRQ and not just one user of it. Thus, if the IRQ is shared, all of the interrupt handlers installed @@ -110,8 +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 @@ -120,4 +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. |