Re: [PATCH] PCI: pciehp: Disable link and turn off slot power while removing

[Mario Limonciello <mario.limonciello@amd.com>]

On 5/6/26 23:26, Lukas Wunner wrote:
> On Wed, May 06, 2026 at 02:16:10PM -0500, Mario Limonciello wrote:
>> On 5/6/26 12:55, Lukas Wunner wrote:
>>> Moreover there are products where Presence Detect is hardwired to zero,
>>> see commit 80696f991424 ("PCI: pciehp: Tolerate Presence Detect hardwired
>>> to zero").  So we have to rely on a link change to detect that a new device
>>> has been plugged in after slot poweroff.  That won't work if the link is
>>> disabled.
>>
>> How would you feel about turning off link detect somewhere specific to the
>> shutdown path?
> 
> I *think* shutdown is performed bottom-up in the hierarchy and so
> this might work.  But it's not great to introduce such a change
> for everyone just because a single product needs it.  

Generally speaking I'm not a fan of Linux changing hardware state and 
not cleaning up after itself at shutdown.  This can lead to weird 
behaviors for power consumption, wakeups, or inconsistent init across a 
kexec vs warm reboot vs cold reboot (that BIOS had a chance to swing 
it's hammer).

> It would
> be better to root-cause the issue.  

I'll see if we can figure out what's happening with traces on a USB 
analyzer.  But FWIW it's a Linux only issue :/

> Maybe the vendor is able to
> provide a BIOS update which resolves it?
> 

Given it's Linux only issue; unlikely.