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    SubjectRe: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs
    On Sat, May 23, 2009 at 6:25 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > On Friday 22 May 2009, Kim Kyuwon wrote:
    >> On Fri, May 22, 2009 at 11:53 AM, Kim Kyuwon <chammoru@gmail.com> 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?
    >> >
    >> > 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.
    >> >
    >> > Regards,
    >> > Kyuwon
    >> >
    >>
    >> I saw resume_device_irqs() is invoked after arch_suspend_enable_irqs()
    >> in your resume code.
    >> So in this gap between resume_device_irqs() and
    >> arch_suspend_enable_irqs(), a few interrupts would be discarded.
    >> i.e, a few data would be lost.
    >>
    >> If keypad wake up the system, first key pressed information would be lost.
    >> If I2C, USB, SPI, UART wake up the system, first a few data would be lost.
    >>
    >> Did you also consider this issue?
    >
    > I think it would happen anyway with the old code, wouldn't it?

    That's not quite right.

    For example, let's assume a keypad device is alive in suspend/resume
    state to wake up the system. Before arch_suspend_enable_irqs(), none
    of keypad irqs is dropped. It is just pending.
    But in your code, a few irqs are discarded due to your resume_device_irqs().

    Regards,
    Kyuwon
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