2009/5/8 Kevin Hilman [off-list ref]:
Arve Hjønnevåg [off-list ref] writes:
quoted
On Thu, May 7, 2009 at 9:19 AM, Kevin Hilman
[off-list ref] wrote:
quoted
From a3f359c66bd0ae1bb2603e7cf120d9d4d68591b7 Mon Sep 17 00:00:00 2001
From: Kevin Hilman <redacted>
Date: Wed, 6 May 2009 16:00:07 -0700
Subject: [PATCH] genirq: ensure IRQs are lazy disabled before suspend
In commit 76d2160147f43f982dfe881404cfde9fd0a9da21, the default
behavior of disable_irq() was changed to delay the disable until it is
next handled.
However, this leaves open the possibility that the system can go into
suspend with an interrupt enabled. For example, if a driver calls
disable_irq() in its suspend_hook there's now a possibility that the
system is suspended before the lazy disable happens.
The result is an unwanted wakeup from suspend if the IRQ is capable of
waking the system (common on embedded SoCs.)
If the interrupt contoller uses the same enable register for wakeup
and interrupts, I think it is the responsibility of the platform code,
not individual drivers, to disable the interrupts that are not marked
for wakeup before entering suspend.
I agree, for wakeup interrupts, drivers should use
[set|disable]_irq_wake() and the platform code should handle this.
I used wakeup interrupts in this description as an example which
turned out to be a bad example. The 2nd version of this patch I
posted, I removed the reference to wakeup interrupts in favor of just
talking about the delayed disable piece.
But ignoring wakup interrupts, would you agree that the delayed
disable of an interrupt should not wait until after resume?
No. The platform code needs to turn off interrupts that are not wakeup
interrupts anyway, so there is not much point in disabling some
interrupts early. Also, if the interrupt in question is not a wakeup
interrupt you leave it in a state where it does not detect an edge. A
driver that enables its hardware in resume, then unmasks the interrupt
would loose an interrupt that triggered between enabling the hardware
and unmasking the interrupt.
quoted
quoted
This patch ensures that the lazy disable is done, and masked by
the irq_chip before the system goes into suspend.
This will create a window where wakeup interrupts can be lost if the
driver has masked the interrupt (by calling disable_irq). If the
hardware does not allow edge detection on disabled interrupts (the msm
platform has this limitation) then this change will turn off the edge
detection. If suspend_ops->enter does not turn the interrupt (and edge
detection) back on (without this change it may never need to turn on
any interrupt) it will not wakeup at all.
Not sure I follow you here...
It seems like you're relying on the delayed disable to wait until
after resume so that disabled interrupts can wake the system. How
did this work before the delayed disable patch?
It did not.
If the interrupt is being used as a wakeup, why would anyone be
calling disable_irq()?
Drivers call disable_irq to make sure their interrupt handler does not
get called. A driver may not be able take interrupts after its suspend
hook has been called. If it calls disable_irq on a wakeup interrupt
then this interrupt should abort suspend or wake up from suspend. The
driver will then see the interrupt when it call enable_irq in its
resume handler.
--
Arve Hjønnevåg
Arve Hjønnevåg [off-list ref] writes:
2009/5/8 Kevin Hilman [off-list ref]:
quoted
Arve Hjønnevåg [off-list ref] writes:
quoted
On Thu, May 7, 2009 at 9:19 AM, Kevin Hilman
[off-list ref] wrote:
quoted
From a3f359c66bd0ae1bb2603e7cf120d9d4d68591b7 Mon Sep 17 00:00:00 2001
From: Kevin Hilman <redacted>
Date: Wed, 6 May 2009 16:00:07 -0700
Subject: [PATCH] genirq: ensure IRQs are lazy disabled before suspend
In commit 76d2160147f43f982dfe881404cfde9fd0a9da21, the default
behavior of disable_irq() was changed to delay the disable until it is
next handled.
However, this leaves open the possibility that the system can go into
suspend with an interrupt enabled. For example, if a driver calls
disable_irq() in its suspend_hook there's now a possibility that the
system is suspended before the lazy disable happens.
The result is an unwanted wakeup from suspend if the IRQ is capable of
waking the system (common on embedded SoCs.)
If the interrupt contoller uses the same enable register for wakeup
and interrupts, I think it is the responsibility of the platform code,
not individual drivers, to disable the interrupts that are not marked
for wakeup before entering suspend.
I agree, for wakeup interrupts, drivers should use
[set|disable]_irq_wake() and the platform code should handle this.
I used wakeup interrupts in this description as an example which
turned out to be a bad example. The 2nd version of this patch I
posted, I removed the reference to wakeup interrupts in favor of just
talking about the delayed disable piece.
But ignoring wakup interrupts, would you agree that the delayed
disable of an interrupt should not wait until after resume?
No. The platform code needs to turn off interrupts that are not wakeup
interrupts anyway, so there is not much point in disabling some
interrupts early. Also, if the interrupt in question is not a wakeup
interrupt you leave it in a state where it does not detect an edge. A
driver that enables its hardware in resume, then unmasks the interrupt
would loose an interrupt that triggered between enabling the hardware
and unmasking the interrupt.
Got it. Thanks for your (repeated) explanations. I understand now
your reasons for allowing the interrupt to remain across suspend. I
will modify my platform to rely on [enable|disable]_irq_wake() in
addition to ensuring platform code is disabling non wakup IRQs.
quoted
quoted
quoted
This patch ensures that the lazy disable is done, and masked by
the irq_chip before the system goes into suspend.
This will create a window where wakeup interrupts can be lost if the
driver has masked the interrupt (by calling disable_irq). If the
hardware does not allow edge detection on disabled interrupts (the msm
platform has this limitation) then this change will turn off the edge
detection. If suspend_ops->enter does not turn the interrupt (and edge
detection) back on (without this change it may never need to turn on
any interrupt) it will not wakeup at all.
Not sure I follow you here...
It seems like you're relying on the delayed disable to wait until
after resume so that disabled interrupts can wake the system. How
did this work before the delayed disable patch?
It did not.
quoted
If the interrupt is being used as a wakeup, why would anyone be
calling disable_irq()?
Drivers call disable_irq to make sure their interrupt handler does not
get called. A driver may not be able take interrupts after its suspend
hook has been called. If it calls disable_irq on a wakeup interrupt
then this interrupt should abort suspend or wake up from suspend. The
driver will then see the interrupt when it call enable_irq in its
resume handler.
OK.
Kevin
Arve Hjønnevåg [off-list ref] writes:
2009/5/8 Kevin Hilman [off-list ref]:
quoted
Arve Hjønnevåg [off-list ref] writes:
quoted
On Thu, May 7, 2009 at 9:19 AM, Kevin Hilman
[off-list ref] wrote:
quoted
From a3f359c66bd0ae1bb2603e7cf120d9d4d68591b7 Mon Sep 17 00:00:00 2001
From: Kevin Hilman <redacted>
Date: Wed, 6 May 2009 16:00:07 -0700
Subject: [PATCH] genirq: ensure IRQs are lazy disabled before suspend
In commit 76d2160147f43f982dfe881404cfde9fd0a9da21, the default
behavior of disable_irq() was changed to delay the disable until it is
next handled.
However, this leaves open the possibility that the system can go into
suspend with an interrupt enabled. For example, if a driver calls
disable_irq() in its suspend_hook there's now a possibility that the
system is suspended before the lazy disable happens.
The result is an unwanted wakeup from suspend if the IRQ is capable of
waking the system (common on embedded SoCs.)
If the interrupt contoller uses the same enable register for wakeup
and interrupts, I think it is the responsibility of the platform code,
not individual drivers, to disable the interrupts that are not marked
for wakeup before entering suspend.
I agree, for wakeup interrupts, drivers should use
[set|disable]_irq_wake() and the platform code should handle this.
I used wakeup interrupts in this description as an example which
turned out to be a bad example. The 2nd version of this patch I
posted, I removed the reference to wakeup interrupts in favor of just
talking about the delayed disable piece.
But ignoring wakup interrupts, would you agree that the delayed
disable of an interrupt should not wait until after resume?
No. The platform code needs to turn off interrupts that are not wakeup
interrupts anyway, so there is not much point in disabling some
interrupts early. Also, if the interrupt in question is not a wakeup
interrupt you leave it in a state where it does not detect an edge. A
driver that enables its hardware in resume, then unmasks the interrupt
would loose an interrupt that triggered between enabling the hardware
and unmasking the interrupt.
Got it. Thanks for your (repeated) explanations. I understand now
your reasons for allowing the interrupt to remain across suspend. I
will modify my platform to rely on [enable|disable]_irq_wake() in
addition to ensuring platform code is disabling non wakup IRQs.
quoted
quoted
quoted
This patch ensures that the lazy disable is done, and masked by
the irq_chip before the system goes into suspend.
This will create a window where wakeup interrupts can be lost if the
driver has masked the interrupt (by calling disable_irq). If the
hardware does not allow edge detection on disabled interrupts (the msm
platform has this limitation) then this change will turn off the edge
detection. If suspend_ops->enter does not turn the interrupt (and edge
detection) back on (without this change it may never need to turn on
any interrupt) it will not wakeup at all.
Not sure I follow you here...
It seems like you're relying on the delayed disable to wait until
after resume so that disabled interrupts can wake the system. How
did this work before the delayed disable patch?
It did not.
quoted
If the interrupt is being used as a wakeup, why would anyone be
calling disable_irq()?
Drivers call disable_irq to make sure their interrupt handler does not
get called. A driver may not be able take interrupts after its suspend
hook has been called. If it calls disable_irq on a wakeup interrupt
then this interrupt should abort suspend or wake up from suspend. The
driver will then see the interrupt when it call enable_irq in its
resume handler.
OK.
Kevin