linux-kernel - Re: [PATCH v2 2/2] ACPI / Sleep: Check low power idle constraints for debug only

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Message-ID: <1502326255.4234.35.camel@linux.intel.com>
Date:   Wed, 09 Aug 2017 17:50:55 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     lenb@...nel.org, linux-pm@...r.kernel.org,
        mario.limonciello@...l.com, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, lukas@...ner.de
Subject: Re: [PATCH v2 2/2] ACPI / Sleep: Check low power idle constraints
 for debug only

On Thu, 2017-08-10 at 01:17 +0200, Rafael J. Wysocki wrote:
> On Wednesday, August 9, 2017 12:41:15 AM CEST Srinivas Pandruvada
> wrote:
> > 
> > For SoC to achieve its lowest power platform idle state a set of
> > hardware
> > preconditions must be met. These preconditions or constraints can
> > be
> > obtained by issuing a device specific method (_DSM) with function
> > "1".
> > Refer to the document provided in the link below.
> > 
> > Here during initialization (from attach() callback of LPS0 device),
> > invoke
> > function 1 to get the device constraints. Each enabled constraint
> > is
> > stored in a table.
> > 
> > The devices in this table are used to check whether they were in
> > required
> > minimum state, while entering suspend. This check is done from
> > platform
> > freeze wake() callback, only when /sys/power/pm_debug_messages
> > attribute
> > is non zero.
> > 
> > If any constraint is not met and device is ACPI power managed then
> > it
> > prints the device name to kernel logs.
> > 
> > Also if debug is enabled in acpi/sleep.c, the constraint table and
> > state
> > of each device on wake is dumped in kernel logs.
> > 
> > Link: http://www.uefi.org/sites/default/files/resources/Intel_ACPI_
> > Low_Power_S0_Idle.pdf
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel
> > .com>
> > ---
> >  drivers/acpi/sleep.c | 162
> > +++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 162 insertions(+)
> > 
> > diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> > index 2b881de..b3ef577 100644
> > --- a/drivers/acpi/sleep.c
> > +++ b/drivers/acpi/sleep.c
> > @@ -669,6 +669,7 @@ static const struct acpi_device_id
> > lps0_device_ids[] = {
> [cut]
> 
> > 
> >  
> > @@ -773,6 +933,8 @@ static void acpi_freeze_wake(void)
> >  	 */
> >  	if (acpi_sci_irq_valid() &&
> >  	    !irqd_is_wakeup_armed(irq_get_irq_data(acpi_sci_irq)))
> > {
> > +		if (pm_debug_messages_enabled())
> > +			lpi_check_constraints();
> I'm not sure why you only want to check the constraints when we do
> the
> _cancel_wakeup() thing.
> 
> IMO the check is relevant regardless of whether or not the wakeup was
> via ACPI.
OK. I will move out of this if block.

Thanks,
Srinivas
> 
> > 
> >  		pm_system_cancel_wakeup();
> >  		s2idle_wakeup = true;
> >  	}
> > 
>