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PCI/ASPM: Fix L1SS saving
Commit 1db806e ("PCI/ASPM: Save parent L1SS config in pci_save_aspm_l1ss_state()") aimed to perform L1SS config save for both the Upstream Port and its upstream bridge when handling an Upstream Port, which matches what the L1SS restore side does. However, parent->state_saved can be set true at an earlier time when the upstream bridge saved other parts of its state. Then later when attempting to save the L1SS config while handling the Upstream Port, parent->state_saved is true in pci_save_aspm_l1ss_state() resulting in early return and skipping saving bridge's L1SS config because it is assumed to be already saved. Later on restore, junk is written into L1SS config which causes issues with some devices. Remove parent->state_saved check and unconditionally save L1SS config also for the upstream bridge from an Upstream Port which ought to be harmless from correctness point of view. With the Upstream Port check now present, saving the L1SS config more than once for the bridge is no longer a problem (unlike when the parent->state_saved check got introduced into the fix during its development). Link: https://lore.kernel.org/r/20250131152913.2507-1-ilpo.jarvinen@linux.intel.com Fixes: 1db806e ("PCI/ASPM: Save parent L1SS config in pci_save_aspm_l1ss_state()") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219731 Reported-by: Niklāvs Koļesņikovs <pinkflames.linux@gmail.com> Reported by: Rafael J. Wysocki <rafael@kernel.org> Closes: https://lore.kernel.org/r/CAJZ5v0iKmynOQ5vKSQbg1J_FmavwZE-nRONovOZ0mpMVauheWg@mail.gmail.com Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> Closes: https://lore.kernel.org/r/d7246feb-4f3f-4d0c-bb64-89566b170671@molgen.mpg.de Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Tested-by: Niklāvs Koļesņikovs <pinkflames.linux@gmail.com> Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> # Dell XPS 13 9360
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drivers/pci/pcie/aspm.c

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@@ -108,9 +108,6 @@ void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
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pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CTL2, cap++);
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pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CTL1, cap++);
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if (parent->state_saved)
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return;
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/*
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* Save parent's L1 substate configuration so we have it for
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* pci_restore_aspm_l1ss_state(pdev) to restore.

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