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

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Message-ID: <20181029095331.GA26118@ulmo>
Date:   Mon, 29 Oct 2018 10:53:31 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Lee Jones <lee.jones@...aro.org>, 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 Fri, Oct 19, 2018 at 02:22:53PM +0100, 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 ...
>  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>
> ---
>  drivers/mfd/tps6586x.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)

Acked-by: Thierry Reding <treding@...dia.com>

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