Re: [PATCH v1 1/3] gpio: Add APM X-Gene standby GPIO controller driver

[Y Vo <yvo@xxxxxxx>]

Hi Arnd,

Per Linus, shall we hold this driver until the GIC submission complete
? Or we will send the version without access GIC to read status in
case the GPIO is configured IRQ ?

+static int xgene_gpio_sb_get(struct gpio_chip *gc, u32 gpio)
+{
+       struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
+       struct xgene_gpio_sb *chip = to_xgene_gpio_sb(mm_gc);
+       u32 data;
+
+       data = ioread32(mm_gc->regs + MPA_GPIO_IN_ADDR);
+
+       return (data &  GPIO_MASK(gpio)) ? 1 : 0;
+}

Regards,
Y

On Wed, Oct 29, 2014 at 5:24 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Wednesday 29 October 2014 10:52:47 Linus Walleij wrote:
>> On Fri, Oct 24, 2014 at 3:46 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>> > On Friday 24 October 2014 14:14:43 Linus Walleij wrote:
>> > See the discussion I had on this. Yes, each line is connected to a
>> > GIC SPI interrupt by itself. I've discussed this with Marc Zyngier
>> > and Thomas Gleixner at the conference last week, and we concluded
>> > that we will need a new generic interface to get data out of the
>> > parent interrupt controller in a proper way. The current implementation
>> > just maps the GIC registers and reads them directly, which of course
>> > is not a proper way to do it.
>>
>> Hmmmmmm. OK shall we hold this driver until the infrastructure
>> issues are resolved?
>
> Y could send a first version that does not support the IRQ lines
> if he wants to speed up the process.
>
>> The following is a recurring pattern among GPIO controllers:
>> the GPIO controller can go offline (asycnhcronous) and while it
>> is offline a secondary logic triggers an IRQ that wakes the system
>> up, however the GPIO logic cannot really "see" that IRQ since
>> it was sleeping when it arrived.
>>
>> Thus a latent IRQ is pending in the wakeup logic. This concept
>> exists in drivers/pinctrl/nomadik/pinctrl-nomadik.c and I strongly
>> prefer to call these "latent irqs" as it's a clear unambigous
>> terminology.
>>
>> So is this a case of latent IRQs pending in the GIC?
>
> I think this case is different, from what I understand, the GPIO
> controller cannot implement gpio_chip->get() for any line that
> is connected to the GIC, and it has to ask the GIC instead.
> This seems independent of the online/offline state of the controller.
>
>         Arnd
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