[from Bjorn's mail] > In Emmanuel's case, we don't get _OSC control, so > pci_disable_link_state() does nothing. Right, but this is true with the specific log I sent to you. Is it possible that another platform / BIOS, we *will* get _OSC control and that pci_disable_link_state() will actually do something? In that case I would prefer not to remove the call to pcie_disable_link_state(). Also - in the log I sent you, we don't get _OSC control, but I can see 'disabling PCIe ASPM" ... and it *is* enabled (since L1 works). So I am kinda scratching my head here... > >> I'm not convinced iwlwifi really needs to disable the link power >> management states in the first place -- the 1a7123cdd9 changelog isn't >> very convincing, and I'm not aware of any reported issues even though >> we're actually leaving them enabled in many cases. >> >> More generally, I don't think the pci_disable_link_state() interface >> is very useful because it often doesn't do what it claims, and the >> caller has no indication. > > The general issue here is that Windows will (as far as we've been able > to determine) never touch ASPM registers unless given PCIe control via > _OSC. Drivers are presumably able to override this by hitting > configuration registers themselves. The pci_disable_link_state() > functions are currently broadly equivalent to the helper functions > provided in the Windows .inf files, and if drivers really want to > disable the control themselves then they can do so. Renaming the > functions to make that clearer, and possibly adding some additional > functions to force the case, may be worthwhile. > > The only time this should be relevant is if (a) the BIOS has enabled L1 > on iwlwifi, (b) the BIOS has disabled ASPM control, and (c) the hardware > doesn't work with L1 enabled. Are there really cases where that's true? > After having read (a bit) about _OSC I can say the following: L1 is a must for the Windows driver - so that it doesn't sounds reasonable that the .inf of the Windows driver for Intel Wireless NICs disables ASPM through _OSC or through any other mechanism. (a) - this is really platform / BIOS dependent, and I can't test all the platform out there (b) - ditto (c) - the HW *should* work with L1 enabled but we may very well have a bug in the driver. I have tried to check the way we initialize the HW and it seems fine, but one never knows. thanks for your time! -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
