Re: [PATCH v2] PCI: pciehp: Fix hotplug on Catlow Lake with unreliable PME status

[Kuppuswamy Sathyanarayanan]

Hi Lukas/Rafael,

On 2/19/2026 1:54 PM, Kuppuswamy Sathyanarayanan wrote:
> Hi,
> 
> On 2/19/2026 3:09 AM, Rafael J. Wysocki wrote:
>> On Thu, Feb 19, 2026 at 9:04 AM Lukas Wunner <lukas@xxxxxxxxx> wrote:
>>>
>>> On Wed, Feb 18, 2026 at 06:33:15PM +0100, Rafael J. Wysocki wrote:
>>>> First, keeping the ports in D0 may gate runtime PC10.  Does it not?
>>>
>>> The Root Port in question is on the PCH.  I'm not sure, does keeping a
>>> PCH Root Port in D0 also prevent PC10 entry or is that only the case
>>> for Root Ports on the CPU die/tile?
>>
>> If it is located in the PCH, it should not gate PC10 if in D0 at least
>> in theory, but it would be good to verify that.
>>
>> Of course, it will still gate S0ix entry through runtime idle, but
>> that's a bit moot if the platform is unable to enter S0ix through
>> runtime idle anyway for other reasons (which is quite likely), or if
>> the power difference between S0ix and PC10 is small.
> 
> I will gather current PC10 and S0ix numbers. If there is a significant
> difference between the two power savings, I will implement the
> pme_is_broken() approach.

I have gathered the test results. S0ix is not a POR for this platform, so
I was unable to collect those numbers. The deepest package  C-state supported
is PC6.

With pm_runtime_disable() keeping the port in D0, I observe approximately 
10% reduction in PC6 residency. Given this power impact, I will proceed with 
the pme_is_broken() approach suggested by Lukas, which allows the port to 
enter D3hot while keeping hotplug interrupts enabled.

I will submit v3 with this implementation. Change log looks like below:


diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
index 1e9158d7bac7..f854ef9551c3 100644
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -260,13 +260,20 @@ static bool pme_is_native(struct pcie_device *dev)
        return pcie_ports_native || host->native_pme;
 }

+static bool pme_is_broken(struct pcie_device *pcie)
+{
+       struct pci_dev *pdev = pcie->port;
+
+       return !!(pdev->dev_flags & PCI_DEV_FLAGS_PME_UNRELIABLE);
+}
+
 static void pciehp_disable_interrupt(struct pcie_device *dev)
 {
        /*
         * Disable hotplug interrupt so that it does not trigger
         * immediately when the downstream link goes down.
         */
-       if (pme_is_native(dev))
+       if (pme_is_native(dev) && !pme_is_broken(dev))
                pcie_disable_interrupt(get_service_data(dev));
 }

@@ -318,7 +325,7 @@ static int pciehp_resume(struct pcie_device *dev)
 {
        struct controller *ctrl = get_service_data(dev);

-       if (pme_is_native(dev))
+       if (pme_is_native(dev) && !pme_is_broken(dev))
                pcie_enable_interrupt(ctrl);

        pciehp_check_presence(ctrl);
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 48946cca4be7..acaa328dff51 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -6380,3 +6380,51 @@ static void pci_mask_replay_timer_timeout(struct pci_dev *pdev)
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_GLI, 0x9750, pci_mask_replay_timer_timeout);
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_GLI, 0x9755, pci_mask_replay_timer_timeout);
 #endif
+
+/*
+ * When a PCIe port is in D3hot, the hotplug driver depends on PME
+ * to wake the port back to D0 and then process any hotplug-related
+ * state changes. On Intel Catlow Lake platforms, PCH PCIe root ports
+ * do not reliably update PME state during D3hot to D0 transitions.
+ *
+ * Mark affected ports with PCI_DEV_FLAGS_PME_UNRELIABLE to keep
+ * hotplug interrupts (HPIE) enabled during D3hot instead of relying on
+ * PME-based wakeup. This allows hotplug events to be delivered via
+ * direct interrupts while still permitting the port to enter D3hot for
@@ -6380,3 +6380,51 @@ static void pci_mask_replay_timer_timeout(struct pci_dev *pdev)
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_GLI, 0x9750, pci_mask_replay_timer_timeout);
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_GLI, 0x9755, pci_mask_replay_timer_timeout);
 #endif
+
+/*
+ * When a PCIe port is in D3hot, the hotplug driver depends on PME
+ * to wake the port back to D0 and then process any hotplug-related
+ * state changes. On Intel Catlow Lake platforms, PCH PCIe root ports
+ * do not reliably update PME state during D3hot to D0 transitions.
+ *
+ * Mark affected ports with PCI_DEV_FLAGS_PME_UNRELIABLE to keep
+ * hotplug interrupts (HPIE) enabled during D3hot instead of relying on
+ * PME-based wakeup. This allows hotplug events to be delivered via
+ * direct interrupts while still permitting the port to enter D3hot for
+ * power savings.
+ *
+ */
+static void quirk_intel_catlow_pcie_pme_unreliable(struct pci_dev *dev)
+{
+       dev->dev_flags |= PCI_DEV_FLAGS_PME_UNRELIABLE;
+       pci_info(dev, "Catlow PCH port: PME unreliable\n");
+}
+/* Apply quirk to Catlow Lake PCH root ports (0x7a30 - 0x7a4b) */
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a30, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a31, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a32, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a33, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a34, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a35, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a36, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a37, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a38, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a39, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a3a, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a3b, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a3c, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a3d, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a3e, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a3f, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a40, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a41, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a42, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a43, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a44, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a45, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a46, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a47, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a48, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a49, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a4a, quirk_intel_catlow_pcie_pme_unreliable);
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x7a4b, quirk_intel_catlow_pcie_pme_unreliable);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 1c270f1d5123..9761351c5d70 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -253,6 +253,8 @@ enum pci_dev_flags {
         * integrated with the downstream devices and doesn't use real PCI.
         */
        PCI_DEV_FLAGS_PCI_BRIDGE_NO_ALIAS = (__force pci_dev_flags_t) (1 << 14),
+       /* Device PME is broken or unreliable */
+       PCI_DEV_FLAGS_PME_UNRELIABLE = (__force pci_dev_flags_t) (1 << 15),
 };





> 
> 
>>
>>> If this does cause a power regression, the pme_is_broken() approach
>>> suggested upthread might be a viable alternative.  It'll allow the
>>> Root Port to go to D3hot but will keep interrupts enabled in the
>>> Slot Control register.
>>
>> Sounds reasonable to me.
> 
> Sounds good. 
> 
>>
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer