Received-SPF: pass (google.com: domain of linux-kernel+bounces-129335-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Date: Wed, 3 Apr 2024 11:31:14 +0300 (EEST)
To: Luke Jones <luke@ljones.dev>
cc: Hans de Goede <hdegoede@redhat.com>, corentin.chary@gmail.com, 
    platform-driver-x86@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 8/9] platform/x86: asus-wmi: Add support for MCU
 powersave
In-Reply-To: <24071185.4csPzL39Zc@fedora>
Message-ID: <42f09e54-5669-2242-28db-240405e7c4bc@linux.intel.com>
References: <20240402022607.34625-1-luke@ljones.dev> <20240402022607.34625-9-luke@ljones.dev> <71426f4c-a44a-cf87-7045-b3f2b3fc240e@linux.intel.com> <24071185.4csPzL39Zc@fedora>
Precedence: bulk
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="8323328-687975693-1712133074=:1449"

  This message is in MIME format.  The first part should be readable text,
  while the remaining parts are likely unreadable without MIME-aware tools.

--8323328-687975693-1712133074=:1449
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: QUOTED-PRINTABLE

On Wed, 3 Apr 2024, Luke Jones wrote:

> On Wednesday, 3 April 2024 12:01:15=E2=80=AFAM NZDT Ilpo J=C3=A4rvinen wr=
ote:
> > On Tue, 2 Apr 2024, Luke D. Jones wrote:
> > > Add support for an MCU powersave WMI call. This is intended to set th=
e
> > > MCU in to a low-power mode when sleeping. This mode can cut sleep pow=
er
> > > use by around half.
> > >=20
> > > Signed-off-by: Luke D. Jones <luke@ljones.dev>
> >=20
> > Hi,
> >=20
> > I fail to follow the logic of the patch here. This patch makes it
> > configurable which is not bad in itself but what is the reason why a us=
er
> > would not always want to cut sleep power usage down? So this sounds lik=
e a
> > feature that the user wants always enabled if available.
> >=20
> > So what are the downsides of enabling it if it's supported?
>=20
> Honestly, I'm not sure. Previously it was a source of issues but with rec=
ent=20
> bios and more work in the various gaming-handheld distros it's much less =
of a=20
> problem. The issue before was that the MCU would appear every second susp=
end=20
> due to the suspend sequence being more parallel compared to windows being=
=20
> sequential - the acpi calls related to this would "unplug" the USB device=
s=20
> that are related to the n-key (keyboard, same internal dev as laptops) an=
d not=20
> complete it before suspend. And then on resume it was unreliable.
>=20
> I worked around this by calling the unplug very early, and trying to "plu=
g"=20
> super early also so that subsystems wouldn't notice the absence of the de=
vice=20
> and create new devices + paths on add. Most of the requirement for that c=
ame=20
> from some userspace programs unable to handle the unplug/plug part, but a=
lso=20
> bad device state occurring.
>=20
> But now with the forced wait for the device to finish its task, and then =
the=20
> forced wait before letting it add itself back everything is fine - althou=
gh it=20
> does mean everything sees a device properly unplugged and plugged.
>=20
> All of the above is to say that the "powersave" function was also part of=
 the=20
> issue as delayed things further and we couldn't add the device back befor=
e=20
> subsystems noticed.
>=20
> Distros like bazzite and chimeraOS are now using this patch, and I'd like=
 to=20
> leave it to them to set a default for now. If it turns out everything is=
=20
> indeed safe as houses then we can adjust the kernel default.
>=20
> A side-note I think is that because there is a forced wait time due to un=
able=20
> to use the right acpi path, the old excuse of "but users might want the d=
evice=20
> to wake faster by turning off powersave" doesn't really apply now.
>=20
> I will discuss with the main stakeholders, but for now can we accept as i=
s? If=20
> changes are required we'll get them done before the merge window.

Yes, I think it is okay to make it configurable first and then look=20
separately into making it default on.

--=20
 i.

--8323328-687975693-1712133074=:1449--