In subject: PCI/ASPM: Document D0 requirement when enabling PCI-PM L1 PM Substates On Fri, Feb 16, 2024 at 02:26:01PM +0800, Jian-Hong Pan wrote: > According to PCI Express Base Specification Revision 6.0, Section 5.5.4: > "If setting either or both of the enable bits for PCI-PM L1 PM Substates, > both ports must be configured as described in this section while in D0." "PCIe r6.0, sec 5.5.4" is enough. > Add notes into pci_enable_link_state(_locked) for kernel-doc. Add note about D0 requirement in pci_enable_link_state() kernel-doc. > Hope these > notify callers ensuring the devices in D0, if PCI-PM L1 PM Substates are > going to be enabled. Skip this part. > Signed-off-by: Jian-Hong Pan <jhp@xxxxxxxxxxxxx> With above updates, Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > --- > v3: > - Fix as readable comments > > v4: > - The same > > drivers/pci/pcie/aspm.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index 7f1d674ff171..a39d2ee744cb 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -1416,6 +1416,9 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked) > * touch the LNKCTL register. Also note that this does not enable states > * disabled by pci_disable_link_state(). Return 0 or a negative errno. > * > + * Note: Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per > + * PCIe r6.0, sec 5.5.4. > + * > * @pdev: PCI device > * @state: Mask of ASPM link states to enable > */ > @@ -1432,6 +1435,9 @@ EXPORT_SYMBOL(pci_enable_link_state); > * can't touch the LNKCTL register. Also note that this does not enable states > * disabled by pci_disable_link_state(). Return 0 or a negative errno. > * > + * Note: Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per > + * PCIe r6.0, sec 5.5.4. > + * > * @pdev: PCI device > * @state: Mask of ASPM link states to enable > * > -- > 2.43.2 >
