Re: [RFC PATCH V2 3/8] genirq: Add runtime power management support for IRQ chips

[Grygorii Strashko <grygorii.strashko@ti.com>]

On 02/05/2016 04:37 PM, Linus Walleij wrote:
> On Thu, Jan 21, 2016 at 8:51 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> 
>> So as long as an interrupt handler is installed, there is no sane way that we
>> can decide to power down the irq chip, unless that chip has the magic ability
>> to relay incoming interrupts while powered down :)
> 
> Actually isn't that exactly what almost every SoC that supports
> deepsleep does?
> 
> They power off the primary interrupt controller and arm the padring
> of the SoC with an asynchronous edge detector to wake up as soon
> as something happens on a few select lines, like a keypad button
> or whatnot.
> 
> The asynchronous edge detector is handled by the ROM or some
> power-management microcontroller, which wakes up the system
> and restores power to the CPU and primary interrupt controller.
> That is the magic ability right there.
> 
> Of course as the wakeup signal may be deasserted at the
> point the system actually comes back up, so the magic ROM
> power management unit then needs to latch
> any latent IRQs from some shadow register to the primary interrupt
> controller, which as far as I've seen is done by out-of-tree hacks
> similar to the irq_[get/set]_irqchip_state() implemented
> by Marc Zyngier, albeit for virtualization.
> 
> I've not seen it on any non-primary interrupt controller though.
> 

OMAP gpio can lose context(Power) even if there
GPIO IRQs configured as wakeup sources (wakeup happen through the SoC specific HW
responsible for wakeup in this case) - pcs.

It also injects IRQs if their triggering type is not fully compatible with PM HW.  

-- 
regards,
-grygorii