mainlining shenanigans
17e5888e4e
Modern x86 laptops are starting to use GPIO pins as interrupts more
and more, e.g. touchpads and touchscreens have almost all moved away
from PS/2 and USB to using I2C with a GPIO pin as interrupt.
Modern x86 laptops also have almost all moved to using s2idle instead
of using the system S3 ACPI power state to suspend.
The Intel and AMD pinctrl drivers do not define irq_retrigger handlers
for the irqchips they register, this is causing edge triggered interrupts
which happen while suspended using s2idle to get lost.
One specific example of this is the lid switch on some devices, lid
switches used to be handled by the embedded-controller, but now the
lid open/closed sensor is sometimes directly connected to a GPIO pin.
On most devices the ACPI code for this looks like this:
Method (_E00, ...) {
Notify (LID0, 0x80) // Status Change
}
Where _E00 is an ACPI event handler for changes on both edges of the GPIO
connected to the lid sensor, this event handler is then combined with an
_LID method which directly reads the pin. When the device is resumed by
opening the lid, the GPIO interrupt will wake the system, but because the
pinctrl irqchip doesn't have an irq_retrigger handler, the Notify will not
happen. This is not a problem in the case the _LID method directly reads
the GPIO, because the drivers/acpi/button.c code will call _LID on resume
anyways.
But some devices have an event handler for the GPIO connected to the
lid sensor which looks like this:
Method (_E00, ...) {
if (LID_GPIO == One)
LIDS = One
else
LIDS = Zero
Notify (LID0, 0x80) // Status Change
}
And the _LID method returns the cached LIDS value, since on open we
do not re-run the edge-interrupt handler when we re-enable IRQS on resume
(because of the missing irq_retrigger handler), _LID now will keep
reporting closed, as LIDS was never changed to reflect the open status,
this causes userspace to re-resume the laptop again shortly after opening
the lid.
The Intel GPIO controllers do not allow implementing irq_retrigger without
emulating it in software, at which point we are better of just using the
generic HARDIRQS_SW_RESEND mechanism rather then re-implementing software
emulation for this separately in aprox. 14 different pinctrl drivers.
Select HARDIRQS_SW_RESEND to solve the problem of edge-triggered GPIO
interrupts not being re-triggered on resume when they were triggered during
suspend (s2idle) and/or when they were the cause of the wakeup.
This requires
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.