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    SubjectRe: [PATCH v1] Input: tegra-kbc - report wakeup key for some platforms.
    Hello Dmitry.
    Please find replies inline.

    On Sun, 2011-12-04 at 00:50 -0800, Dmitry Torokhov wrote:
    > Hi Rakesh,
    > On Thu, Dec 01, 2011 at 01:09:59PM -0800, Rakesh Iyer wrote:
    > > Hello Dmitry.
    > >
    > > Sorry for the wrap issue, my Outlook does not seem to obey the settings.
    > >
    > > I wanted to explain the tegra system resume path implementation so I can justify
    > > why I am doing this complicated fix and why I feel it will guarantee the resume
    > > is due to keypress.
    > >
    > > The tegra wake resume code is registered as a syscore ops.
    > > When the system is resumed due to a wake event, the suspend_enter (after wakeup)
    > > routine will invoke the tegra syscoreops_resume method and that routine will propagate
    > > the wake event to the individual ISR's through genirq.
    > > If kbc was wake source, kbc_isr will be invoked in this execution path.
    > >
    > > If system is resumed due to other reason, the tegra_syscoreops_resume code will not
    > > find the event.
    > Consider the following sequence:
    > 1. Something other than keyboard generates wakeup event
    > 2. It's IRQ fires up and gets serviced
    At this point syscoreops_resume has finished all its wakeup processing.

    > 3. System starts resuming devices
    > 4. User presses a key on the keypad while it is still suspended _and_
    > registered as a wakeup source
    This will have no impact on the system and keypad ISR will not be
    > 5. Keypad's ISR runs as well and you decide that KEY_POWER should be
    > reported even though keypad wasn't the real reason the system
    > woke up.
    The interrupt line we use to detect wakeup processing is the keypress
    interrupt which is disabled and will never cause the ISR invocation from
    a device interrupt(i.e. the PIC).

    In other words KBC isr gets invoked for 2 reasons
    a) FIFO interrupt is generated, which will not happen as long as
    scanning logic is disabled until kbc_resume executes.
    b) The syscoreops_resume codepath calls into the ISR after finding KBC
    was a wakesource. If this happens it will happen only when the kernel
    resumes from its suspend code path.
    > Is this scenario not possible?
    > Thanks.
    With that being the case do you think the fix makes sense?


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