On 9/11/25 8:43 AM, Rafael J. Wysocki wrote:
On Thu, Sep 11, 2025 at 3:34 PM Mario Limonciello <superm1@xxxxxxxxxx> wrote:
On 9/11/25 8:11 AM, Lukas Wunner wrote:
In 2012, commit dbf0e4c7257f ("PCI: EHCI: fix crash during suspend on ASUS
computers") amended pci_pm_suspend_noirq() to work around a BIOS issue by
clearing the Command register if the suspended device is a USB EHCI host
controller.
Commit 0b68c8e2c3af ("PCI: EHCI: Fix crash during hibernation on ASUS
computers") subsequently amended pci_pm_poweroff_noirq() to do the same.
Two years later, commit 7d2a01b87f16 ("PCI: Add pci_fixup_suspend_late
quirk pass") introduced the ability to execute arbitrary quirks
specifically in pci_pm_suspend_noirq() and pci_pm_poweroff_noirq().
This allows moving the ASUS workaround out of generic code and into a
proper quirk to improve maintainability and readability. Constrain to x86
since the ASUS BIOS doesn't seem to have been used on other arches.
lspci output of affected EHCI host controllers reveals that the only bits
set in the Command register are Memory Space Enable and Bus Master Enable:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=658778
The latter is cleared by:
hcd_pci_suspend()
suspend_common()
pci_disable_device()
pci_disable_device() does not clear I/O and Memory Space Enable, although
its name suggests otherwise.
That was my gut reaction as well.
The kernel has never disabled these bits
once they're enabled. Doing so would avoid the need for the quirk, but it
is unclear what will break if this fundamental behavior is changed.
It's too late for this cycle to do so, but how would you feel about
making this change at the start of the next cycle so it had a whole
cycle to bake in linux-next and see if there is a problem in doing so?
One cycle in linux-next may not be sufficient I'm afraid because
linux-next is not tested on the majority of systems running Linux.
We'd probably learn about the breakage from distro vendors.
If there is it could certainly be moved back to a quirk.
Most likely, it would work on the majority of systems, but there would
be a tail of systems where it would break. That tail would then need
to be quirked somehow and it may be worse than just one quirk we have
today.
But is that a reason not to *try* and rid the tech debt?
We could just all agree that *if* there is breakage we revert back to
the quirk just for EHCI.
