On Thu, Oct 12, 2023 at 03:53:39PM +0300, Ilpo Järvinen wrote: > On Wed, 11 Oct 2023, Bjorn Helgaas wrote: > > On Mon, Sep 18, 2023 at 04:10:55PM +0300, Ilpo Järvinen wrote: > > > pci_disable_link_state() lacks a symmetric pair. Some drivers want to > > > disable ASPM during certain phases of their operation but then > > > re-enable it later on. If pci_disable_link_state() is made for the > > > device, there is currently no way to re-enable the states that were > > > disabled. > > > > pci_disable_link_state() gives drivers a way to disable specified ASPM > > states using a bitmask (PCIE_LINK_STATE_L0S, PCIE_LINK_STATE_L1, > > PCIE_LINK_STATE_L1_1, etc), but IIUC the driver can't tell exactly > > what changed and can't directly restore the original state, e.g., > > > > - PCIE_LINK_STATE_L1 enabled initially > > - driver calls pci_disable_link_state(PCIE_LINK_STATE_L0S) > > - driver calls pci_enable_link_state(PCIE_LINK_STATE_L0S) > > - PCIE_LINK_STATE_L0S and PCIE_LINK_STATE_L1 are enabled now > > > > Now PCIE_LINK_STATE_L0S is enabled even though it was not initially > > enabled. Maybe that's what we want; I dunno. > > > > pci_disable_link_state() currently returns success/failure, but only > > r8169 and mt76 even check, and only rtl_init_one() (r8169) has a > > non-trivial reason, so it's conceivable that it could return a bitmask > > instead. > > It's great that you suggested this since it's actually what also I've been > started to think should be done instead of this straightforward approach > I used in V2. > > That is, don't have the drivers to get anything directly from LNKCTL > but they should get everything through the API provided by the > disable/enable calls which makes it easy for the driver to pass the same > value back into the enable call. > > > > Add pci_enable_link_state() to remove ASPM states from the state > > > disable mask. > > > > > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> > > > --- > > > drivers/pci/pcie/aspm.c | 42 +++++++++++++++++++++++++++++++++++++++++ > > > include/linux/pci.h | 2 ++ > > > 2 files changed, 44 insertions(+) > > > > > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > > > index 91dc95aca90f..f45d18d47c20 100644 > > > --- a/drivers/pci/pcie/aspm.c > > > +++ b/drivers/pci/pcie/aspm.c > > > @@ -1117,6 +1117,48 @@ int pci_disable_link_state(struct pci_dev *pdev, int state) > > > } > > > EXPORT_SYMBOL(pci_disable_link_state); > > > > > > +/** > > > + * pci_enable_link_state - Re-enable device's link state > > > + * @pdev: PCI device > > > + * @state: ASPM link states to re-enable > > > + * > > > + * Enable device's link state that were previously disable so the link is > > > > "state[s] that were previously disable[d]" alludes to the use case you > > have in mind, but I don't think it describes how this function > > actually works. This function just makes it possible to enable the > > specified states. The @state parameter may have nothing to do with > > any previously disabled states. > > Yes, it's what I've been thinking between the lines. But I see your point > that this API didn't make it easy/obvious as is. > > Would you want me to enforce it too besides altering the API such that the > states are actually returned from disable call? (I don't personally find > that necessary as long as the API pair itself makes it obvious what the > driver is expect to pass there.) This was just a comment about the doc not matching the function behavior. I think we have to support pci_enable_link_state() even if the driver hasn't previously called pci_disable_link_state(), so drivers have to be able to specify the pci_enable_link_state() @state from scratch. Does that answer the enforcement question? I don't think we can really enforce anything other than that @state specifies valid ASPM states. Bjorn
