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

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Date:	Sun, 4 Dec 2011 00:50:38 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Rakesh Iyer <riyer@...dia.com>
Cc:	"rydberg@...omail.se" <rydberg@...omail.se>,
	Stephen Warren <swarren@...dia.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v1] Input: tegra-kbc - report wakeup key for some
 platforms.

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
3. System starts resuming devices
4. User presses a key on the keypad while it is still suspended _and_
   registered as a wakeup source
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.

Is this scenario not possible?

Thanks.

-- 
Dmitry
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