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    SubjectRE: [PATCH v1] Input: tegra-kbc - report wakeup key for some platforms.

    ________________________________________
    From: Dmitry Torokhov [dmitry.torokhov@gmail.com]
    Sent: Sunday, December 04, 2011 8:27 PM
    To: Rakesh Iyer
    Cc: rydberg@euromail.se; Stephen Warren; Laxman Dewangan; linux-kernel@vger.kernel.org; linux-input@vger.kernel.org; linux-tegra@vger.kernel.org
    Subject: Re: [PATCH v1] Input: tegra-kbc - report wakeup key for some platforms.

    On Sun, Dec 04, 2011 at 05:18:17PM -0800, riyer wrote:
    > 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
    > invoked.
    > > 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 code already in mainline or still somewhere else?

    I think this code has not made it to mainline yet.
    Its in the Android and ChromeOs kernel trees.

    > >
    > > Is this scenario not possible?
    > >
    > > Thanks.
    > >
    > With that being the case do you think the fix makes sense?

    >> OK, yes. I do not think it is that important if we occasionally report
    >> KEY_POWER even if KBC was not a true wakeup source but that's fine.

    >>Thanks.

    >>--
    >> Dmitry

    So can I assume this patch is accepted?

    Thanks and Regards
    Rakesh

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