Re: [PATCH] mfd: tps6586x: Handle interrupts on suspend

From: Dmitry Osipenko <digetx@gmail.com>
To: Jon Hunter <jonathanh@nvidia.com>,
	Thierry Reding <thierry.reding@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>,
	linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] mfd: tps6586x: Handle interrupts on suspend
Date: Wed, 24 Oct 2018 15:44:17 +0300	[thread overview]
Message-ID: <3e79e753-4e63-5bf0-c9ff-40547d053c8a@gmail.com> (raw)
In-Reply-To: <72b80285-d6ff-9cb9-3bcd-bb3d92006323@nvidia.com>

On 10/24/18 1:49 PM, Jon Hunter wrote:
> 
> On 22/10/2018 12:19, Dmitry Osipenko wrote:
>> On 10/22/18 12:52 PM, Thierry Reding wrote:
>>> On Fri, Oct 19, 2018 at 02:22:53PM +0100, Jon Hunter wrote:
>>>> From: Jonathan Hunter <jonathanh@nvidia.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@vger.kernel.org
>>>>
>>>> Signed-off-by: Jon Hunter <jonathanh@nvidia.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?
>>
>> What is the expected behaviour of IRQ disabling? Should it disable wakeup ability or only mask IRQ handling?
> 
> I believe only mask the interrupt. However, the caveat here could be if
> the parent interrupt controller actually supports wake-up. For Tegra it
> is the LIC that handles the wake-up.
> 
>> Couple months ago disabling of IRQ was disabling the wakeup, now something has been changed in kernel and wakeup isn't getting disabled. So either there was a bug before that was fixed or there is a bug now.
> 
> Are you sure you were disabling the PMIC host interrupt? If you disable
> the RTC interrupt in the PMIC's RTC driver, then this will prevent the
> wake-up from occurring because you are masking the interrupt within the
> PMIC and so it will never generate an interrupt to the host.

I'm pretty sure (but not 100%) that was trying the same change as in your patch and it didn't work sometime before. If disable_irq() shouldn't disable wakeup, then everything is perfect now.