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    SubjectRe: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs
    On Sat, May 23, 2009 at 7:29 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > On Saturday 23 May 2009, Kim Kyuwon wrote:
    >> On Sat, May 23, 2009 at 6:23 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    >> > On Friday 22 May 2009, Kim Kyuwon wrote:
    >> >> On Wed, May 6, 2009 at 8:27 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    >> >> > On Wednesday 06 May 2009, Kevin Hilman wrote:
    >> >> >> Arve Hjønnevåg <arve@android.com> writes:
    >> >> >>
    >> >> >> > On Tue, May 5, 2009 at 8:52 AM, Kevin Hilman
    >> >> >> > <khilman@deeprootsystems.com> wrote:
    >> >> >> >> Andrew Morton <akpm@linux-foundation.org> writes:
    >> >> >> >>
    >> >> >> >>> On Mon,  4 May 2009 17:27:04 -0700 Kevin Hilman <khilman@deeprootsystems.com> wrote:
    >> >> >> >>>
    >> >> >> >>>> Interrupts that are flagged as wakeup sources via set_irq_wake()
    >> >> >> >>>> should not be disabled for suspend.
    >> >> >> >>>>
    >> >> >> >>>
    >> >> >> >>> Why not?
    >> >> >> >>>
    >> >> >> >>
    >> >> >> >> If an interrupt is a wakeup source, and it is disabled at the chip
    >> >> >> >> level, it will no longer generate interrupts, and thus no longer wake
    >> >> >> >> up the system.
    >> >> >> >>
    >> >> >> >> I'd be interested in hearing why wakeup interrupts should be disabled
    >> >> >> >> during suspend.
    >> >> >
    >> >> > That depends on whether or not they are used for anything else than wake-up.
    >> >> >
    >> >> >>
    >> >> >> [...]
    >> >> >>
    >> >> >> >>>
    >> >> >> >>> If this fixes some bug then please provide a description of that bug?
    >> >> >> >>
    >> >> >> >> The bug is that on TI OMAP, interrupts that are used for wakeup events
    >> >> >> >> are disabled by this code causing the system to no longer wake up.
    >> >> >> >
    >> >> >> > What do you do if the interrupt triggers right after your driver has
    >> >> >> > returned from its late suspend hook?
    >> >> >>
    >> >> >> If it's a wakeup IRQ, I assume you want it to prevent suspend.
    >> >> >>
    >> >> >> But I don't see how that can happen in the current code. IIUC, by the
    >> >> >> time your late suspend hook is run, your device IRQ is already
    >> >> >> disabled, so it won't trigger an interrupt that will be caught by
    >> >> >> check_wakeup_irqs() anyways.
    >> >> >
    >> >> > My understanding of __disable_irq() was that it didn't actually disable the
    >> >> > IRQ at the hardware level, allowing the CPU to actually receive the interrupt
    >> >> > and acknowledge it, but preventing the device driver for receiving it.  Does
    >> >> > it work differently on the affected systems?
    >> >>
    >> >> Hi, Rafael.
    >> >> Sorry for bring the old issue but please let me ask you about
    >> >> suspend_device_irqs() function.
    >> >>
    >> >> __disable_irq() disables the IRQ at the hardware level in the
    >> >> following irq_chips
    >> >>
    >> >> i8259A_chip
    >> >> i8259_pic
    >> >> i8259A_chip
    >> >> bfin_internal_irqchip
    >> >> crisv10_irq_type
    >> >> crisv32_irq_type
    >> >> h8300irq_chip
    >> >> m_irq_chip
    >> >> mn10300_cpu_pic_level
    >> >> xtensa_irq_chip
    >> >> iop13xx_msi_chip
    >> >> msi_irq
    >> >>
    >> >> Because these irq_chips mask interrupts in 'disable' hook.
    >> >>
    >> >> Thus, your suspend_device_irqs() function disables all IRQs at the
    >> >> hardware level on all architectures which use irq_chips listed above
    >> >> in suspend state.
    >> >> Is this really what you wanted?
    >> >
    >> > What we wanted was to resolve specific issue related to the handling of
    >> > interrupts during suspend and resume which caused observable breakage and
    >> > from the point of view of fixing this issue it doesn't really matter whether or
    >> > not interrupts are masked in the disable hook.
    >> >
    >> >> If interrupt can wake up the system from suspend in some architectures
    >> >> and if disable_irq_wake is not supported in these architectures, I
    >> >> wonder if suspend_device_irqs() don't allow waking up by interrupt.
    >> >
    >> > I think that the platforms that may be affected by this issue will have to take
    >> > care of it.
    >>
    >> You changed the really important part of Linux, which may affect most
    >> processor architectures. I think you should be careful. If some of
    >> architectures can't take care of it (they can implement
    >> disable_irq_wake correctly in H/W level, will you revert your changes?
    >
    > No, the changes are not going to be reverted.  In fact things should have been
    > done like this already much earlier.
    >
    > Now, do you have any particular example of a problem related to these changes
    > or is it only a theoretical issue?

    I'd CCing you when I'm sending a mail for this particular example of a example.
    http://markmail.org/thread/fvt7d62arofon5xx

    Regards,
    Kyuwon
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