From: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> Unlike ACPI based platforms, there are no known issues with D3Hot for the PCI bridges in Device Tree based platforms. Past discussions (Link [1]) determined the restrictions around D3 should be relaxed for all Device Tree systems. So let's allow the PCI bridges to go to D3Hot during runtime. To match devm_pci_alloc_host_bridge() -> devm_of_pci_bridge_init(), we look at the host bridge's parent when determining whether this is a Device Tree based platform. Not all bridges have their own node, but the parent (controller) should. Link: https://lore.kernel.org/linux-pci/20240227225442.GA249898@bhelgaas/ [1] Link: https://lore.kernel.org/linux-pci/20240828210705.GA37859@bhelgaas/ [2] Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> [Brian: look at host bridge's parent, not bridge node; rewrite description] Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx> --- Based on prior work by Manivannan Sadhasivam that was part of a bigger series that stalled: [PATCH v5 4/4] PCI: Allow PCI bridges to go to D3Hot on all Devicetree based platforms https://lore.kernel.org/linux-pci/20240802-pci-bridge-d3-v5-4-2426dd9e8e27@xxxxxxxxxx/ I'm resubmitting this single patch, since it's useful and seemingly had agreement. I massaged it a bit to relax some restrictions on how the Device Tree should look. Changes in v5: - Pulled out of the larger series, as there were more controversial changes in there, while this one had agreement (Link [2]). - Rewritten with a relaxed set of rules, because the above patch required us to modify many device trees to add bridge nodes. drivers/pci/pci.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index e278861684bc..5d898f5ea155 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3018,6 +3018,8 @@ static const struct dmi_system_id bridge_d3_blacklist[] = { */ bool pci_bridge_d3_possible(struct pci_dev *bridge) { + struct pci_host_bridge *host_bridge; + if (!pci_is_pcie(bridge)) return false; @@ -3038,6 +3040,15 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) if (pci_bridge_d3_force) return true; + /* + * Allow D3 for all Device Tree based systems. We assume a host + * bridge's parent will have a device node, even if this bridge + * may not have its own. + */ + host_bridge = pci_find_host_bridge(bridge->bus); + if (dev_of_node(host_bridge->dev.parent)) + return true; + /* Even the oldest 2010 Thunderbolt controller supports D3. */ if (bridge->is_thunderbolt) return true; -- 2.47.0.338
