On 6/2/2023 6:19 PM, Bjorn Helgaas wrote:
On Fri, Jun 02, 2023 at 05:38:37PM -0500, Limonciello, Mario wrote:
On 6/2/2023 5:20 PM, Bjorn Helgaas wrote:
On Tue, May 30, 2023 at 11:39:47AM -0500, Mario Limonciello wrote:
Using a USB keyboard or mouse to wakeup the system from s2idle fails when
that xHCI device is connected to a USB-C port for an AMD USB4 router.
It sounds like the real issue is that "Root Ports in D3hot/D3cold may
not support wakeup", and the USB, xHCI, USB-C, AMD USB4 router bits
are probably not really relevant. And hopefully even the "AMD
platforms" mentioned below is not relevant.
Yeah. It comes down to how much you want in the commit
about how we got to this conclusion versus a generic
fix. I generally like to be verbose about a specific case
something fixes so that when distros decide what to pull
in to their older maintenance kernels they can understand
what's important.
That's actually my point. I think this problem probably affects
non-USB devices, non-xHCI devices, non-USB4 routers, etc.
If we can say "Any device below a Root Port in D3hot/D3cold may not
support wakeup if X, Y, Z. Root Ports may be put in D3hot/D3cold for
sleep/hibernate/s2idle/...", that's much more actionable.
Completely agree.
Due to commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
all PCIe ports go into D3 during s2idle.
When specific root ports are put into D3 over s2idle on some AMD platforms
it is not possible for the platform to properly identify wakeup sources.
This happens whether the root port goes into D3hot or D3cold.
Can we connect this to a spec so it's not just the empirical "some AMD
platforms work like X" observation?
"s2idle" is meaningful on the power management side of the house, but
it doesn't appear in PCI or ACPI specs, so I don't know what it means
here. I assume the D3hot/D3cold state of the Root Port is the
critical factor, regardless of how it got there.
Unfortunately (?) for this particular issue it's only a
critical factor when the system is in s2idle.
PME works fine to wake up the device if the root port is
in either D3hot or D3cold when the system isn't in s2idle.
So that must mean something other than the Root Port has to be in some
specific state. "System in s2idle" is not actionable in terms of PCI
maintenance. It sounds like we just haven't really gotten to the root
cause yet.
The root cause of this behavior is deep in the platform
firmware. This is why the platform firmware doesn't
advertise power management support for the root port.
Linux shouldn't assume root ports support D3 just because they're on a
machine newer than 2015, the ports should also be deemed power manageable.
Add an extra check explicitly for root ports to ensure D3 isn't selected
for them if they are not power-manageable through platform firmware.
But I *would* like to know specifically what "power manageable" means
here. I might naively assume that a device with the PCI Power
Management Capability is "power manageable", and that if PME_Support
includes D3hot and D3cold, we're good to go. But obviously it's more
complicated than that, and I'd like to cite the spec that mentions the
actual things we need here.
Power manageable through platform firmware means the device
has ACPI methods like like _PR0, _PS0.
What's the connection to wakeup?
There is also no _PRW (power resources for wake) for this
root port.
+ * It's not safe to put root ports that don't support power
+ * management into D3.
I assume "it's not safe" really means "Root Ports in D3hot/D3cold may
not be able to signal PME interrupts unless ... <mumble> platform
firmware <mumble> e.g., ACPI method <mumble> ..."
Can we include some of those hints here?
I'm cautious about hardcoding logic used by
acpi_bus_get_power_flags() in a comment in case it changes.
How about:
"Root ports in D3 may not be able to reliably signal wakeup
events unless platform firmware signals power management
capabilities".
I'm really looking hard for that spec citation :) Without that, this
just devolves into "this seems to work on these systems."
I mean that's exactly what the broken logic below this
fix is....
But I think I can get you what you're looking for.
From this failing system the problematic root port is GP19.
The DSDT has:
Device (GP19) {
Method (_DSM,..)
Method (_PRT,..)
Device (NHI0)
Device (NHI1)
}
The SSDT has:
Scope (\_SB.PCI0.GP19) {
Method (YS0W,..)
Method (YPRW,..)
Method (RPRM,..)
Method (WPRM,..)
Method (SPDP,..)
Method (SPCH,..)
Method (_STA,..)
Method (_INI,..)
Method (_REG,..)
}
Section 7.3 from the ACPI spec [1] says
"For a device that is power-managed using ACPI, a Definition Block
contains one or more of the objects found in the table below. Power
management of a device is done using Power Resource control"
The GP19 device has NONE of the objects mentioned in the table.
Outside of this change, I do think this means acpi_bus_get_power_flags()
may want to also look for some of the other objects besides _PS0 and
_PR0 to resolve that a device is power manageable though.
[1]
https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/07_Power_and_Performance_Mgmt/device-power-management-objects.html?highlight=pr0#device-power-management-objects
+ */
+ if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT &&
+ !platform_pci_power_manageable(bridge))
+ return false;
+
/*
* It should be safe to put PCIe ports from 2015 or newer
* to D3.
--
2.34.1
