On some X86 devices we do not register an input-device, because the
power-button is also handled by the soc_button_array (GPIO) input driver,
and we want to avoid reporting power-button presses to userspace twice.

Sofar when we did this we also did not register our interrupt handlers,
since those were only necessary to report input events.

But on at least 2 device models the Medion Akoya E1239T and the GPD win,
the GPIO pin used by the soc_button_array driver for the power-button
cannot wakeup the system from suspend. Why this does not work is not clear,
I've tried comparing the value of all relevant registers on the Cherry
Trail SoC, with those from models where this does work. I've checked:
PMC registers: FUNC_DIS, FUNC_DIS2, SOIX_WAKE_EN, D3_STS_0, D3_STS_1,
D3_STDBY_STS_0, D3_STDBY_STS_1; PMC ACPI I/O regs: PM1_STS_EN, GPE0a_EN
and they all have identical contents in the working and non working cases.
I suspect that the firmware either sets some unknown register to a value
causing this, or that it turns off a power-plane which is necessary for
GPIO wakeups to work during suspend.

What does work on the Medion Akoya E1239T is letting the AXP288 wakeup
the system on a power-button press (the GPD win has a different PMIC).

Move the registering of the power-button press/release interrupt-handler
from axp20x_pek_probe_input_device() to axp20x_pek_probe() so that the
PMIC will wakeup the system on a power-button press, even if we do not
register an input device.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20200426155757.297087-1-hdegoede@redhat.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>