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| author | Mark Rutland <mark.rutland@arm.com> | 2015-02-20 14:53:46 +0000 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2015-02-26 01:17:53 +0100 |
| commit | 737eb0301f296d55c22350c6968ff1ef51bacb5f (patch) | |
| tree | 63c2256c8a57d581ecde81156a8607af939dfe22 /Documentation/power | |
| parent | c517d838eb7d07bbe9507871fab3931deccff539 (diff) | |
| download | lwn-737eb0301f296d55c22350c6968ff1ef51bacb5f.tar.gz lwn-737eb0301f296d55c22350c6968ff1ef51bacb5f.zip | |
genirq / PM: better describe IRQF_NO_SUSPEND semantics
The IRQF_NO_SUSPEND flag is intended to be used for interrupts required
to be enabled during the suspend-resume cycle. This mostly consists of
IPIs and timer interrupts, potentially including chained irqchip
interrupts if these are necessary to handle timers or IPIs. If an
interrupt does not fall into one of the aforementioned categories,
requesting it with IRQF_NO_SUSPEND is likely incorrect.
Using IRQF_NO_SUSPEND does not guarantee that the interrupt can wake the
system from a suspended state. For an interrupt to be able to trigger a
wakeup, it may be necessary to program various components of the system.
In these cases it is necessary to use {enable,disabled}_irq_wake.
Unfortunately, several drivers assume that IRQF_NO_SUSPEND ensures that
an IRQ can wake up the system, and the documentation can be read
ambiguously w.r.t. this property.
This patch updates the documentation regarding IRQF_NO_SUSPEND to make
this caveat explicit, hopefully making future misuse rarer. Cleanup of
existing misuse will occur as part of later patch series.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/suspend-and-interrupts.txt | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/Documentation/power/suspend-and-interrupts.txt b/Documentation/power/suspend-and-interrupts.txt index 2f9c5a5fcb25..50493c9284b4 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 |