linux-kernel - Re: platform/x86: asus-wmi: SW_TABLET

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Message-ID: <20200904171743.ejew22p3zzada55p@fastboi.localdomain>
Date:   Fri, 4 Sep 2020 19:17:43 +0200
From:   Samuel Čavoj <samuel@...oj.net>
To:     Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Corentin Chary <corentin.chary@...il.com>
Cc:     acpi4asus-user@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: platform/x86: asus-wmi: SW_TABLET_MODE is always 1 on some
 devices

Hi,

On 04.09.2020 12:06, Hans de Goede wrote:
> Hi,
> 
> On 9/4/20 11:45 AM, Samuel Čavoj wrote:
> > Hello!
> > 
> > On 02.09.2020 14:52, Samuel Čavoj wrote:
> > > Hello,
> > > 
> > > On 02.09.2020 13:52, Hans de Goede wrote:
> > > > But I would rather try to figure out a better way. Can you
> > > > create an acpidump, by as root running:
> > > > 
> > > > acpidump -o acpidump.asus-UX360CA
> > > 
> > > The file is attached gzipped.
> > > 
> > > > 
> > > > And then send me a direct (so without including the list)
> > > > email with the generated acpidump.asus-UX360CA file attached please?
> > > > 
> > > > Also, if necessary are you capable of building your own
> > > > kernel with a (test)patch applied ?
> > > 
> > > Yes, that is no problem at all.
> > > Thank you for your quick response.
> > > 
> > > Regards,
> > > Samuel
> > 
> > I don't mean to waste your time, it's just that my trust in mail systems
> > has been steadily decreasing. I would just like to make sure you have
> > received my previous email with the acpidump.
> > 
> > In case not, here[1] it is available over https, if the message got
> > dropped because of the attachment.
> 
> I got your mail, but I've been burried under a ton of work,
> so it may take a couple of days at least before I can take
> a closer look at this.

That's quite alright.

I decided I would try and see if I can be of any use, so I looked around
in the WMI implementation in the DSDT and found the following in the
DSTS method:

[...]
37486     If ((IIA0 == 0x00120063))
37487     {
37488         Local0 = ^^PCI0.LPCB.EC0.DKPS ()
37489         If ((Local0 == One))
37490         {
37491             Return (0x00010001)
37492         }                                                                                                
37493         Else
37494         {
37495             Return (0x00010000)
37496         }
37497     }
[...]

This is the If statement responsible for the ASUS_WMI_DEVID_KBD_DOCK
device, and it always seems to return 0x00010000 on my machine. I
followed it up the call chain but in the end it just read some bit from
some register of the EC.

Then I noticed the If statement right above it, which corresponds to
dev_id 0x00060062:

[...]
37472     If ((IIA0 == 0x00060062))
37473     {
37474         If (^^PCI0.LPCB.EC0.RPIN (0x15))
37475         {
37476             Local0 = 0x00010001
37477         }
37478         Else
37479         {
37480             Local0 = 0x00010000
37481         }
37482
37483         Return (Local0)
37484     }
[...]

By a stroke of luck, it turns out it's the correct one! I patched the
driver to query the state on every event and print it out, and it is
exactly what we are looking for.

The state is 0 if the device is in normal, laptop state and changes to 1
if flipped over 180 degrees. I patched the module so that the
SW_TABLET_MODE switch was set according to it, and everything seems to
be behaving as it should. This is, of course, not a full solution, as we
still somehow need to decide whether to use the KDB_DOCK device or this
one. I don't know what to do about that. Ideally find some flag in the
ACPI which says which one we should use?

The event code which is fired when the lid switch state changes, as we
already know from the sparse keymap[1], is 0xfa. When the laptop is
suspended in laptop mode, flipped to tablet mode in its sleep and
awoken, the event is fired. It is, however, not fired when doing it the
other way around, so we should probably check the state on resume as
well.

Please don't hesitate to ask for any additional testing or information
required from my side.

Regards,
Sam

P.S.: I'm adding back the lists and other people I addressed initially.

[1]: https://lore.kernel.org/patchwork/patch/973647/