Re: [REGRESSION] Intel Wireless adapter is not detected until suspending to RAM and resuming

[Lukas Wunner <lukas@wunner.de>]

On Wed, Oct 22, 2025 at 05:30:25PM +0200, Lukas Wunner wrote:
> Looking at the ASPM configuration in the lspci output you've provided,
> I note that after booting without 4d4c10f763d7, ASPM is disabled on
> the Root Port but L1 is enabled on the Wifi card!
> 
> After resuming from system sleep, ASPM is disabled on both of them
> (with and without 4d4c10f763d7).
> 
> I suspect the incongruence of ASPM settings between Root Port and
> Wifi card is the root cause of the Presence Detect Changed flaps
> as well as the Correctable Errors.  I guess the BIOS set these
> incorrectly.  Looking at the code in:
> 
> pcie_aspm_init_link_state()
>   pcie_aspm_cap_init()
> 
> ... it first disables L0s and L1 to initialize L1 substates,
> then restores the register values as they were set by BIOS.
> This feels wrong.  The safest option is probably to instead
> disable L0s and/or L1 if either of them was only enabled
> on one of the two link partners.

Below is a completely untested patch to force ASPM to the
intersection of the two link partners, thus fixing incongruent
BIOS settings.  Does it help on a kernel with 4d4c10f763d7?
If it does, what's the behavior if applied to a kernel without
4d4c10f763d7?

I tried to find errata on the Intel AC 7265 "Stone Peak" wifi card
and instead found this document which explains that only L1 and
not L0s is supported:

https://fcc.report/FCC-ID/2AVBM-GK5/5728379.pdf

Thanks,

Lukas

-- >8 --

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 7cc8281..7fd3eda 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -830,8 +830,8 @@ static void pcie_aspm_override_default_link_state(struct pcie_link_state *link)
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 {
 	struct pci_dev *child = link->downstream, *parent = link->pdev;
+	u16 parent_lnkctl, child_lnkctl, common_lnkctl;
 	u32 parent_lnkcap, child_lnkcap;
-	u16 parent_lnkctl, child_lnkctl;
 	struct pci_bus *linkbus = parent->subordinate;
 
 	if (blacklist) {
@@ -900,6 +900,12 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	/* Restore L0s/L1 if they were enabled */
 	if (FIELD_GET(PCI_EXP_LNKCTL_ASPMC, child_lnkctl) ||
 	    FIELD_GET(PCI_EXP_LNKCTL_ASPMC, parent_lnkctl)) {
+		common_lnkctl = FIELD_GET(PCI_EXP_LNKCTL_ASPMC, child_lnkctl) &
+				FIELD_GET(PCI_EXP_LNKCTL_ASPMC, parent_lnkctl);
+		parent_lnkctl &= ~PCI_EXP_LNKCTL_ASPMC;
+		parent_lnkctl |= common_lnkctl;
+		child_lnkctl &= ~PCI_EXP_LNKCTL_ASPMC;
+		child_lnkctl |= common_lnkctl;
 		pcie_capability_write_word(parent, PCI_EXP_LNKCTL, parent_lnkctl);
 		pcie_capability_write_word(child, PCI_EXP_LNKCTL, child_lnkctl);
 	}