On Tue, Apr 2, 2013 at 4:49 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > On Tuesday, April 02, 2013 10:30:54 AM Bjorn Helgaas wrote: >> On Tue, Apr 2, 2013 at 9:02 AM, Martin Mokrejs >> <mmokrejs@xxxxxxxxxxxxxxxxxx> wrote: >> > Hi Ying, >> > >> > huang ying wrote: >> >> >> And please give me the full dmesg for boot and incremental dmesg for >> >> operations. >> > >> > >> > The incremental bits here, the full dmesg will send only directly to your email, due to its size. >> >> Is there a bugzilla for this issue? Please attach the complete dmesg >> there or somewhere similar so we can all benefit. >> >> I think we have two problems that may be relevant to this discussion. >> >> 1) The _OSC "PCI Express Capability Structure control" bit. I don't >> think Linux pays attention to whether the BIOS has granted us control >> over the capability, so we may do things to it that the BIOS doesn't >> expect. > > Yes, it does, as far as I can say. Let me expand on this to see if we're talking about the same thing. I'm looking at Tables 6-149 and 6-150 in ACPI spec 5.0, and I interpret them as saying the OS should not perform any configuration in the PCI Express, VC, Power Budgeting, AER, or Serial Number capabilities unless the BIOS grants "PCI Express Capability Structure control." I see the code in acpi_pci_root_add() that runs _OSC with OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL in flags, but I don't see anything that uses the result to decide whether we can write to the Device Control, Link Control, Slot Control, etc., registers in the capability, or to the other extended capabilities. (ASPM is an exception -- we *do* call pcie_no_aspm(), and maybe that keeps us from touching the ASPM part of Link Control.) I haven't looked deeply enough to identify a problem; it's just something that worries me. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
