gpio: omap: fix irq triggering in smart-idle wakeup mode

gpio: omap: fix irq triggering in smart-idle wakeup mode

Now GPIO IRQ loss is observed on dra7-evm after suspend/resume cycle
in the following case:
  extcon_usb1(id_irq) ->  pcf8575.gpio1 -> omapgpio6.gpio11 -> gic

the extcon_usb1 is wake up source and it enables IRQ wake up for
id_irq by calling enable/disable_irq_wake() during suspend/resume
which, in turn, causes execution of omap_gpio_wake_enable(). And
omap_gpio_wake_enable() will set/clear corresponding bit in
GPIO_IRQWAKEN_x register.

omapgpio6 configuration after boot - wakeup is enabled for GPIO IRQs
by default from  omap_gpio_irq_type:
GPIO_IRQSTATUS_SET_0    | 0x00000400
GPIO_IRQSTATUS_CLR_0    | 0x00000400
GPIO_IRQWAKEN_0         | 0x00000400
GPIO_RISINGDETECT       | 0x00000000
GPIO_FALLINGDETECT      | 0x00000400

omapgpio6 configuration after after suspend/resume cycle:
GPIO_IRQSTATUS_SET_0    | 0x00000400
GPIO_IRQSTATUS_CLR_0    | 0x00000400
GPIO_IRQWAKEN_0         | 0x00000000 <---
GPIO_RISINGDETECT       | 0x00000000
GPIO_FALLINGDETECT      | 0x00000400

As result, system will start to lose interrupts from pcf8575 GPIO
expander, because when OMAP GPIO IP is in smart-idle wakeup mode, there
is no guarantee that transition(s) on input non wake up GPIO pin will
trigger asynchronous wake-up request to PRCM and then IRQ generation.
IRQ will be generated when GPIO is in active mode - for example, some
time after accessing GPIO bank registers IRQs will be generated
normally, but issue will happen again once PRCM will put GPIO in low
power smart-idle wakeup mode.

Note 1. Issue is not reproduced if debounce clk is enabled for GPIO
bank.

Note 2. Issue hardly reproducible if GPIO pins group contains both
wakeup/non-wakeup gpios - for example, it will be hard to reproduce
issue with pin2 if GPIO_IRQWAKEN_0=0x1 GPIO_IRQSTATUS_SET_0=0x3
GPIO_FALLINGDETECT = 0x3 (TRM "Power Saving by Grouping the Edge/Level
Detection").

Note 3. There nothing common bitween System wake up and OMAP GPIO bank
IP wake up logic - the last one defines how the GPIO bank ON-IDLE-ON
transition will happen inside SoC under control of PRCM.

Hence, fix the problem by removing omap_set_gpio_wakeup() function
completely and so keeping always in sync GPIO IRQ mask/unmask
(IRQSTATUS_SET) and wake up enable (GPIO_IRQWAKEN) bits; and adding
IRQCHIP_MASK_ON_SUSPEND flag in OMAP GPIO irqchip. That way non wakeup
GPIO IRQs will be properly masked/unmask by IRQ PM core during
suspend/resume cycle.

Cc: Roger Quadros <rogerq@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>