linux-kernel - Re: [PATCH] mfd: as3722: Handle interrupts on suspend

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Message-ID: <20151120103018.GD3098@x1>
Date:	Fri, 20 Nov 2015 10:30:18 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH] mfd: as3722: Handle interrupts on suspend

On Fri, 20 Nov 2015, Jon Hunter wrote:

> 
> On 19/11/15 14:23, Jon Hunter wrote:
> > The as3722 device is registered as an irqchip and the as3722-rtc interrupt
> > is one of it's interrupt sources. When using the as3722-rtc as a wake-up
> > device from suspend, the following is seen:
> > 
> >   PM: Syncing filesystems ... done.
> >   Freezing user space processes ... (elapsed 0.001 seconds) done.
> >   Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
> >   Suspending console(s) (use no_console_suspend to debug)
> >   PM: suspend of devices complete after 161.119 msecs
> >   PM: late suspend of devices complete after 1.048 msecs
> >   PM: noirq suspend of devices complete after 0.756 msecs
> >   Disabling non-boot CPUs ...
> >   CPU1: shutdown
> >   CPU2: shutdown
> >   CPU3: shutdown
> >   Entering suspend state LP1
> >   Enabling non-boot CPUs ...
> >   CPU1 is up
> >   CPU2 is up
> >   CPU3 is up
> >   PM: noirq resume of devices complete after 0.487 msecs
> >   as3722 4-0040: Failed to read IRQ status: -16
> >   as3722 4-0040: Failed to read IRQ status: -16
> >   as3722 4-0040: Failed to read IRQ status: -16
> >   as3722 4-0040: Failed to read IRQ status: -16
> >   ...
> > 
> > The reason why the as3722 interrupt status cannot be read is because the
> > as3722 interrupt is not masked during suspend and when the as3722-rtc
> > interrupt occurs, to wake-up the device, the interrupt is seen before the
> > i2c controller has been resumed in order to read the as3722 interrupt
> > status.
> > 
> > The as3722-rtc driver sets it's interrupt as a wake-up source during
> > suspend, which gets propagated to the parent as3722 interrupt. However,
> > the as3722-rtc driver cannot disable it's interrupt during suspend
> > otherwise we would never be woken up and so the as3722 must disable it's
> > interrupt instead.
> > 
> > Fix this by disabling the as3722 interrupt during suspend. To ensure that
> > a wake-up event from the as3722 is not missing, enable the as3722 interrupt
> > as a wake-up source before disabling the interrupt on entering suspend.
> > 
> > Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> > ---
> >  drivers/mfd/as3722.c | 29 +++++++++++++++++++++++++++++
> >  1 file changed, 29 insertions(+)
> > 
> > diff --git a/drivers/mfd/as3722.c b/drivers/mfd/as3722.c
> > index 924ea90494ae..8ee6e4008276 100644
> > --- a/drivers/mfd/as3722.c
> > +++ b/drivers/mfd/as3722.c
> > @@ -405,6 +405,8 @@ static int as3722_i2c_probe(struct i2c_client *i2c,
> >  		goto scrub;
> >  	}
> >  
> > +	device_init_wakeup(as3722->dev, true);
> > +
> >  	dev_dbg(as3722->dev, "AS3722 core driver initialized successfully\n");
> >  	return 0;
> >  
> > @@ -422,6 +424,28 @@ static int as3722_i2c_remove(struct i2c_client *i2c)
> >  	return 0;
> >  }
> >  
> > +static int as3722_i2c_suspend(struct device *dev)
> > +{
> > +	struct as3722 *as3722 = dev_get_drvdata(dev);
> > +
> > +	if (device_may_wakeup(dev))
> > +		enable_irq_wake(as3722->chip_irq);
> > +	disable_irq(as3722->chip_irq);
> > +
> > +	return 0;
> > +}
> > +
> > +static int as3722_i2c_resume(struct device *dev)
> > +{
> > +	struct as3722 *as3722 = dev_get_drvdata(dev);
> > +
> > +	if (device_may_wakeup(dev))
> > +		disable_irq_wake(as3722->chip_irq);
> > +	enable_irq(as3722->chip_irq);
> 
> I just realised that I should enable the irq before disabling the wakeup
> here. I will fix that.
> 
> I will wait to send out a V2 for a couple days in case there are any
> other comments.

Easier for everyone if you just resend.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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