RE: [PATCH v1] Input: tegra-kbc - report wakeup key for some platforms.
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________________________________________ From: Dmitry Torokhov [dmitry.torokhov@xxxxxxxxx] Sent: Sunday, December 04, 2011 8:27 PM To: Rakesh Iyer Cc: rydberg@xxxxxxxxxxx; Stephen Warren; Laxman Dewangan; linux-kernel@xxxxxxxxxxxxxxx; linux-input@xxxxxxxxxxxxxxx; linux-tegra@xxxxxxxxxxxxxxx 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-- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html