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Date:	Tue, 6 Oct 2015 15:43:08 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [RFC][PATCH v3 3/3] input: i8042: Avoid resetting controller on
 system suspend/resume

On Wed, Oct 07, 2015 at 01:08:30AM +0200, Rafael J. Wysocki wrote:
> On Tuesday, October 06, 2015 03:34:42 PM Dmitry Torokhov wrote:
> > On Wed, Oct 07, 2015 at 12:53:49AM +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > If the upcoming system suspend is not going to be handled by the
> > > platform firmware, like in the suspend-to-idle case, it is not
> > > necessary to reset the controller in i8042_pm_suspend(), so avoid
> > > doing that.
> > > 
> > > Moreover, if the system resume currently in progress has not been
> > > started by the platform firmware, like in the suspend-to-idle case,
> > > i8042_controller_resume() need not be called by i8042_pm_resume(),
> > > so avoid doing that too in that case.
> > > 
> > > Additionally, try to catch the event that woke up the system by
> > > calling the interrupt handler early during system resume if it has
> > > not been started by the platform firmware.
> > > 
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > ---
> > >  drivers/input/serio/i8042.c |   15 +++++++++++++--
> > >  1 file changed, 13 insertions(+), 2 deletions(-)
> > > 
> > > Index: linux-pm/drivers/input/serio/i8042.c
> > > ===================================================================
> > > --- linux-pm.orig/drivers/input/serio/i8042.c
> > > +++ linux-pm/drivers/input/serio/i8042.c
> > > @@ -24,6 +24,7 @@
> > >  #include <linux/platform_device.h>
> > >  #include <linux/i8042.h>
> > >  #include <linux/slab.h>
> > > +#include <linux/suspend.h>
> > >  
> > >  #include <asm/io.h>
> > >  
> > > @@ -1170,7 +1171,8 @@ static int i8042_pm_suspend(struct devic
> > >  {
> > >  	int i;
> > >  
> > > -	i8042_controller_reset(true);
> > > +	if (pm_suspend_via_firmware())
> > > +		i8042_controller_reset(true);
> > >  
> > >  	/* Set up serio interrupts for system wakeup. */
> > >  	for (i = 0; i < I8042_NUM_PORTS; i++) {
> > > @@ -1183,6 +1185,14 @@ static int i8042_pm_suspend(struct devic
> > >  	return 0;
> > >  }
> > >  
> > > +static int i8042_pm_resume_noirq(struct device *dev)
> > > +{
> > > +	if (!pm_resume_via_firmware())
> > > +		i8042_interrupt(0, NULL);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  static int i8042_pm_resume(struct device *dev)
> > >  {
> > >  	int i;
> > > @@ -1199,7 +1209,7 @@ static int i8042_pm_resume(struct device
> > >  	 * to bring it in a sane state. (In case of S2D we expect
> > >  	 * BIOS to reset the controller for us.)
> > >  	 */
> > > -	return i8042_controller_resume(true);
> > > +	return pm_resume_via_firmware() ? i8042_controller_resume(true) : 0;
> > 
> > What happens if we were going to suspend via firmware so we reset the
> > controller but then we got wakeup condition and we actually did not
> > suspend. What pm_resume_via_firmware() will return in this case?
> 
> It will return 'false'.  Do we need to resume the controller then?

Yes.

>  But I guess
> 'false' should be passed to i8042_controller_resume() in that case?

Yes, we do not need to reset the controller in this case, just
reactivate multiplexing mode, etc.

Thanks.

-- 
Dmitry
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