From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Mario Limonciello <mario.limonciello@outlook.com>,
Andreas Noever <andreas.noever@gmail.com>,
Michael Jamet <michael.jamet@intel.com>,
Yehezkel Bernat <YehezkelShB@gmail.com>,
linux-usb <linux-usb@vger.kernel.org>
Subject: Re: Disabling intel-wmi-thunderbolt on devices without Thunderbolt / detecting if a device has Thunderbolt
Date: Mon, 25 Oct 2021 18:12:39 +0300 [thread overview]
Message-ID: <YXbJZ+qP7s7TZ4rQ@lahna> (raw)
In-Reply-To: <b067d9f8-4d15-ac5e-3f1f-ff2ffa3b29aa@redhat.com>
On Mon, Oct 25, 2021 at 04:54:41PM +0200, Hans de Goede wrote:
> > Yes that's exactly what is supposed to happen that this attribute is made.
> > What exactly happens when you write into it?
>
> The _SB.CGWR ACPI method gets called, with arguments coming from ACPI
> settings stored in memory. Depending on those settings this function
> either directly pokes some MMIO or tries to talk to an I2C GPIO
> expander which is not present on the Surface Go, causing it to
> MMIO poke an I2C controller which it should not touch.
>
> In either case the AML code ends up poking stuff it should not touch
> and the entire force_power sysfs attribute should simply not be
> there on devices without thunderbolt.
That's right - it should not be there in the first place if there is no
Thunderbolt controller on that thing.
I guess most of the systems that have this actually do support
Thunderbolt so maybe we can work this around by quirking all the Surface
models in that driver?
next prev parent reply other threads:[~2021-10-25 15:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-25 13:48 Disabling intel-wmi-thunderbolt on devices without Thunderbolt / detecting if a device has Thunderbolt Hans de Goede
2021-10-25 14:46 ` Oliver Neukum
[not found] ` <PH0PR15MB4992B80415BE9BD4836CF336E1839@PH0PR15MB4992.namprd15.prod.outlook.com>
2021-10-25 14:54 ` Hans de Goede
2021-10-25 15:12 ` Mika Westerberg [this message]
2021-10-26 8:17 ` Hans de Goede
2021-10-26 8:53 ` Mika Westerberg
2021-10-26 10:34 ` Hans de Goede
2021-10-26 12:22 ` Mika Westerberg
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