[Bug 295251] Power button does not work on HP Laptop 15s (new module to poll GPIO and raise ACPI event)

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=295251

            Bug ID: 295251
           Summary: Power button does not work on HP Laptop 15s (new
                    module to poll GPIO and raise ACPI event)
           Product: Base System
           Version: 15.0-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: rz@fabmicro.ru

Created attachment 270664
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=270664&action=edit
FreeBSD Kernel Module for monitoring state of Power Button connected to AMD
GPIO

Hi all.

Recently I convinced a friend of mine to install FreeBSD 15.0 on his not so old
HP Laptop Model 15s-eq1337ur based on AMD Ryzen 3 4300 CPU. Things went more or
less fine, WiFi and GPU graphics worked out of the box. But, soon we discovered
that system does not react to Power Button presses. I tried to fast-fix that
with hw.acpi.power_button_state=S4, but that did not work. I noticed, that it
was possible to shutdown the system with sending ACPI event via "acpiconf -s
4". I looked through dmesg for ACPI errors, but did not find anything
suspicious. Frustrated, yet engaged I borrowed this laptop from my friend for a
couple of weeks and began to dive deep into ACPI rabit hole in a hope to find a
simple solution. Fortunately solution has been found, but it's not as simple as
I hoped.

After dumping and disassembling AML tables using acpidump and iasl and spending
two weeks analyzing ASL code and tracing ACPI events I came to the following:

1. Power Button on this HP laptop is connected to AMD GPIO pin 0.

2. ACPI firmware heavily relies on \_SB.GPIO._EVT method being called by system
GPIO driver to process button events (power, sleep and some others). This event
never comes, nobody in the system calls _EVT.

3. FreeBSD supports AMD GPIO since 2018 by amdgpio module.

4. amdgpio module does not support interrupts because interrupts are also not
supported in upstream gpiobus module which relies on INTRNG framework that was
never implemented for PC (amd64) platform. And it seems it won't be implemented
any time soon.

I also analyzed how ACPI works on my own Lenovo Ideapad laptop. The power
button there also connected to GPIO pin 0 and it works fine. After
disassembling and analyzing AML firmware I figured out that it works way
different: it relies on EC0 controller that triggers hardware IRQ9 which is
then processed by fixed button driver (sys/dev/acpica/acpi_button.c).

My initial idea for repairing button on HP laptop was to rewrite and recompile
ASL code in a way similar to what I have on Lenovo. Unfortunately, this task
appeared to be too complex for my two-weeks study of ACPI. So I dropped that
idea and took some other approach: to "prosthetize" missing interrupt from GPIO
pin by polling it.

So, here's my simple Power Button driver/module named gpiopwrb. It binds to
gpiobus, acquires GPIO pin provided by hint and runs a kthread to constantly
poll pin state once in a 1/4 of a second. As pin state changes, it calls to
ACPI method provided by another hint (default is \_SB.GPIO._EVT). This driver
works both on HP and Lenovo laptops on FreeBSD 13.5, 14.3 and 15.0.

Hope this can be of help to other owners of contemporary HP laptops with
Hardware-Reduced ACPI firmware. This driver becomes obsolete soon as interrupt
support is added to gpiobus and amdgpio drivers.

HP Laptop Model 15s-eq1337ur (ProductID 461U9EA#ACB) with the following
firmware:

[000h 0000 004h]                   Signature : "FACP"    [Fixed ACPI
Description Table (FADT)]
[004h 0004 004h]                Table Length : 00000114
[008h 0008 001h]                    Revision : 06
[009h 0009 001h]                    Checksum : FF
[00Ah 0010 006h]                      Oem ID : "HPQOEM"
[010h 0016 008h]                Oem Table ID : "SLIC-MPC"
[018h 0024 004h]                Oem Revision : 01072009
[01Ch 0028 004h]             Asl Compiler ID : "HP  "
[020h 0032 004h]       Asl Compiler Revision : 00010013

Link to repository: https://github.com/pointcheck/gpiopwrb.git

PS: This is my first touch on writing a FreeBSD driver inspired by recent book
by Edson Brandi. ;-)

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