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

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Date:   Mon, 22 Oct 2018 11:52:57 +0200
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(+)

So does this mean that the SPI interrupt for the PMIC can still be a
wakeup source even if it is masked? This is slightly odd because now
you're saying that this does work while it doesn't work for the RTC
interrupt. So is this an implementation quirk of the LIC/GIC on Tegra
which doesn't extend to the TPS6586x? Or am I missing something?

Thierry

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