6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ilpo Järvinen ilpo.jarvinen@linux.intel.com
[ Upstream commit 3e40aa29d47e231a54640addf6a09c1f64c5b63f ]
__pci_reset_bus() calls pci_bridge_secondary_bus_reset() to perform the reset and also waits for the Secondary Bus to become again accessible. __pci_reset_bus() then calls pci_bus_restore_locked() that restores the PCI devices connected to the bus, and if necessary, recursively restores also the subordinate buses and their devices.
The logic in pci_bus_restore_locked() does not take into account that after restoring a device on one level, there might be another Link Downstream that can only start to come up after restore has been performed for its Downstream Port device. That is, the Link may require additional wait until it becomes accessible.
Similarly, pci_slot_restore_locked() lacks wait.
Amend pci_bus_restore_locked() and pci_slot_restore_locked() to wait for the Secondary Bus before recursively performing the restore of that bus.
Fixes: 090a3c5322e9 ("PCI: Add pci_reset_slot() and pci_reset_bus()") Link: https://lore.kernel.org/r/20240808121708.2523-1-ilpo.jarvinen@linux.intel.co... Signed-off-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/pci.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 8db214d4b1d46..c20ce49eecc94 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5598,8 +5598,10 @@ static void pci_bus_restore_locked(struct pci_bus *bus)
list_for_each_entry(dev, &bus->devices, bus_list) { pci_dev_restore(dev); - if (dev->subordinate) + if (dev->subordinate) { + pci_bridge_wait_for_secondary_bus(dev, "bus reset"); pci_bus_restore_locked(dev->subordinate); + } } }
@@ -5633,8 +5635,10 @@ static void pci_slot_restore_locked(struct pci_slot *slot) if (!dev->slot || dev->slot != slot) continue; pci_dev_restore(dev); - if (dev->subordinate) + if (dev->subordinate) { + pci_bridge_wait_for_secondary_bus(dev, "slot reset"); pci_bus_restore_locked(dev->subordinate); + } } }