On Tue, Nov 26, 2024 at 03:17:11PM -0800, Brian Norris wrote: > 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> Thanks for picking it up! - Mani > --- > 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 > -- மணிவண்ணன் சதாசிவம்
