linux-kernel - Re: [Patch 1/1] Input: edt-ft5x06 - disable irq handling during suspend

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Date:   Mon, 24 Jun 2019 07:24:57 -0500
From:   Benoit Parrot <bparrot@...com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Henrik Rydberg <rydberg@...math.org>,
        Marco Felsch <m.felsch@...gutronix.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-input <linux-input@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 1/1] Input: edt-ft5x06 - disable irq handling during
 suspend

Dmitry Torokhov <dmitry.torokhov@...il.com> wrote on Sat [2019-Jun-22 22:59:40 -0700]:
> On Sat, Jun 22, 2019 at 01:37:10PM +0300, Andy Shevchenko wrote:
> > On Fri, Jun 21, 2019 at 9:53 PM Benoit Parrot <bparrot@...com> wrote:
> > >
> > > As a wakeup source when the system is in suspend there is little point
> > > trying to access a register across the i2c bus as it is probably still
> > > inactive. We need to prevent the irq handler from being called during
> > > suspend.
> > >
> > 
> > Hmm... But how OS will know what the event to handle afterwards?
> > I mean shouldn't we guarantee somehow the delivery of the event to the
> > input, in this case, subsystem followed by corresponding user space?
> 
> If we are using level interrupts then it will work OK, however it is
> really easy to lose edge here, as replaying disabled edge triggered
> interrupts is not really reliable.
> 
> Benoit, what kind of interrupt do you use in your system?

Dmitry,

On our systems we currently used edge trigger. One example is available in
mainline: arch/arm/boot/dts/am437x-sk-evm.dts
632:              interrupts = <31 IRQ_TYPE_EDGE_FALLING>;


Benoit

> 
> Thanks.
> 
> -- 
> Dmitry