linux-kernel - Re: [PATCH v2 1/1] irqchip: exynos-combiner: Save IRQ enable set on suspend

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Message-ID: <557AC23D.8040602@collabora.co.uk>
Date:	Fri, 12 Jun 2015 13:27:57 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Sudeep Holla <sudeep.holla@....com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Jason Cooper <jason@...edaemon.net>,
	Chanho Park <parkch98@...il.com>,
	Doug Anderson <dianders@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kukjin Kim <kgene@...nel.org>,
	Peter Chubb <peter.chubb@...ta.com.au>,
	Shuah Khan <shuahkhan@...il.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/1] irqchip: exynos-combiner: Save IRQ enable set
 on suspend

Hello Sudeep,

Thanks a lot for the feedback.

On 06/12/2015 12:10 PM, Sudeep Holla wrote:
> 
> 
> On 12/06/15 06:43, Javier Martinez Canillas wrote:
>> The Exynos interrupt combiner IP loses its state when the SoC enters
>> into a low power state during a Suspend-to-RAM. This means that if a
>> IRQ is used as a source, the interrupts for the devices are disabled
>> when the system is resumed from a sleep state so are not triggered.
>>
>> Save the interrupt enable set register for each combiner group and
>> restore it after resume to make sure that the interrupts are enabled.
>>
> 
> Not sure if you need this. IMO it's not clean and redundant though I
> admit many drivers do exactly same thing. I am trying to remove or point
> out those redundant code as irqchip core has options/flags to do what
> you need. I assume there are no wakeup sources connected to this

Yes, there are wakeup sources connected to this combiner. As Krzysztof
said some wakeup sources use a GPIO line as IRQ whose interrupt parent
is the combiner. As an example the Power gpio-key and cros_ec keyboard
for both Exynos5250 Snow and Exynos5420 Peach Pit/Pi.

Both drivers/input/keyboard/gpio_keysc and drivers/mfd/cros_ec.c do the
right thing though and call {enable,disable}_irq_wake() on the S2R path.

And in fact, the peripherals resume the system after a suspend but after
resume, interrupts are not triggered anymore.

> combiner. Setting irqchip flags should solve this problem. A simple
> patch below should do the job ?
>

I don't see how the below patch is going to work for the case I'm trying to
solve. If I understand correctly, the IRQCHIP_MASK_ON_SUSPEND flag is used
to force masking non wakeup interrupt in the suspend path (instead of just
disabling the interrupts on suspend and not masking at the hardware level)

But my problem is not about interrupts needed to be masked on suspend but
the opposite, that interrupts have to be unmasked on resume since the IP
loses its state so after a resume, interrupts are not triggered anymore.

So I also don't see how implementing irq_set_wake() as you suggested is
going to work. Maybe we need a IRQCHIP_UNMASK_ON_RESUME flag for this case?

> -->8
> 
> diff --git a/drivers/irqchip/exynos-combiner.c 
> b/drivers/irqchip/exynos-combiner.c
> index 5945223b73fa..c0bcec59f829 100644
> --- a/drivers/irqchip/exynos-combiner.c
> +++ b/drivers/irqchip/exynos-combiner.c
> @@ -111,6 +111,7 @@ static struct irq_chip combiner_chip = {
>   #ifdef CONFIG_SMP
>          .irq_set_affinity       = combiner_set_affinity,
>   #endif
> +       .flags                  = IRQCHIP_MASK_ON_SUSPEND,
>   };
> 
> 

Best regards,
Javier
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