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l1kbjorn-helgaas
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PCI: pciehp: Ignore belated Presence Detect Changed caused by DPC
Commit c3be50f ("PCI: pciehp: Ignore Presence Detect Changed caused by DPC") sought to ignore Presence Detect Changed events occurring as a side effect of Downstream Port Containment. The commit awaits recovery from DPC and then clears events which occurred in the meantime. However if the first event seen after DPC is Data Link Layer State Changed, only that event is cleared and not Presence Detect Changed. The object of the commit is thus defeated. That's because pciehp_ist() computes the events to clear based on the local "events" variable instead of "ctrl->pending_events". The former contains the events that had occurred when pciehp_ist() was entered, whereas the latter also contains events that have accumulated while awaiting DPC recovery. In practice, the order of PDC and DLLSC events is arbitrary and the delay in-between can be several milliseconds. So change the logic to always clear PDC events, even if they come after an initial DLLSC event. Fixes: c3be50f ("PCI: pciehp: Ignore Presence Detect Changed caused by DPC") Reported-by: Lương Việt Hoàng <[email protected]> Reported-by: Joel Mathew Thomas <[email protected]> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219765#c165 Signed-off-by: Lukas Wunner <[email protected]> Signed-off-by: Bjorn Helgaas <[email protected]> Tested-by: Lương Việt Hoàng <[email protected]> Tested-by: Joel Mathew Thomas <[email protected]> Link: https://patch.msgid.link/d9c4286a16253af7e93eaf12e076e3ef3546367a.1750257164.git.lukas@wunner.de
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drivers/pci/hotplug/pciehp_hpc.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -771,7 +771,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
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u16 ignored_events = PCI_EXP_SLTSTA_DLLSC;
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if (!ctrl->inband_presence_disabled)
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ignored_events |= events & PCI_EXP_SLTSTA_PDC;
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ignored_events |= PCI_EXP_SLTSTA_PDC;
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events &= ~ignored_events;
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pciehp_ignore_link_change(ctrl, pdev, irq, ignored_events);

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