linux-kernel - Re: [PATCH] mfd: tps6586x: Handle interrupts on suspend

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Message-ID: <20181113075256.GE29388@dell>
Date:   Tue, 13 Nov 2018 07:52:56 +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,
        Dmitry Osipenko <digetx@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mfd: tps6586x: Handle interrupts on suspend

On Mon, 05 Nov 2018, Jon Hunter wrote:

> Hi Lee,
> 
> On 19/10/2018 14:22, Jon Hunter wrote:
> > From: Jonathan Hunter <jonathanh@...dia.com>
> > 
> > The tps6586x driver creates an irqchip that is used by its various child
> > devices for managing interrupts. The tps6586x-rtc device is one of its
> > children that uses the tps6586x irqchip. When using the tps6586x-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.
> >  OOM killer disabled.
> >  Freezing remaining freezable tasks ... (elapsed 0.000 seconds) done.
> >  Disabling non-boot CPUs ...Hi 
> >  Entering suspend state LP1
> >  Enabling non-boot CPUs ...
> >  CPU1 is up
> >  tps6586x 3-0034: failed to read interrupt status
> >  tps6586x 3-0034: failed to read interrupt status
> > 
> > The reason why the tps6586x interrupt status cannot be read is because
> > the tps6586x interrupt is not masked during suspend and when the
> > tps6586x-rtc interrupt occurs, to wake-up the device, the interrupt is
> > seen before the i2c controller has been resumed in order to read the
> > tps6586x interrupt status.
> > 
> > The tps6586x-rtc driver sets it's interrupt as a wake-up source during
> > suspend, which gets propagated to the parent tps6586x interrupt.
> > However, the tps6586x-rtc driver cannot disable it's interrupt during
> > suspend otherwise we would never be woken up and so the tps6586x must
> > disable it's interrupt instead.
> > 
> > Prevent the tps6586x interrupt handler from executing on exiting suspend
> > before the i2c controller has been resumed by disabling the tps6586x
> > interrupt on entering suspend and re-enabling it on resuming from
> > suspend.
> > 
> > Cc: stable@...r.kernel.org
> > 
> > Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> > ---
> 
> Thierry and Dmitry have acked/reviewed this, let me know if you have any
> comments.

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-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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