genirq / PM: describe IRQF_COND_SUSPEND
With certain restrictions it is possible for a wakeup device to share
an IRQ with an IRQF_NO_SUSPEND user, and the warnings introduced by
commit cab303be91
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@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
parent
2c7af5ba65
commit
7438b633a6
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@ -112,8 +112,9 @@ any special interrupt handling logic for it to work.
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IRQF_NO_SUSPEND and enable_irq_wake()
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-------------------------------------
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There are no valid reasons to use both enable_irq_wake() and the IRQF_NO_SUSPEND
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flag on the same IRQ.
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There are very few valid reasons to use both enable_irq_wake() and the
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IRQF_NO_SUSPEND flag on the same IRQ, and it is never valid to use both for the
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same device.
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First of all, if the IRQ is not shared, the rules for handling IRQF_NO_SUSPEND
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interrupts (interrupt handlers are invoked after suspend_device_irqs()) are
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@ -122,4 +123,13 @@ handlers are not invoked after suspend_device_irqs()).
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Second, both enable_irq_wake() and IRQF_NO_SUSPEND apply to entire IRQs and not
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to individual interrupt handlers, so sharing an IRQ between a system wakeup
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interrupt source and an IRQF_NO_SUSPEND interrupt source does not make sense.
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interrupt source and an IRQF_NO_SUSPEND interrupt source does not generally
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make sense.
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In rare cases an IRQ can be shared between a wakeup device driver and an
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IRQF_NO_SUSPEND user. In order for this to be safe, the wakeup device driver
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must be able to discern spurious IRQs from genuine wakeup events (signalling
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the latter to the core with pm_system_wakeup()), must use enable_irq_wake() to
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ensure that the IRQ will function as a wakeup source, and must request the IRQ
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with IRQF_COND_SUSPEND to tell the core that it meets these requirements. If
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these requirements are not met, it is not valid to use IRQF_COND_SUSPEND.
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