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    Subject[157/205] PCI/PM: Do not use native PCIe PME by default
    2.6.34-stable review patch.  If anyone has any objections, please let us know.


    From: Rafael J. Wysocki <>

    commit b27759f880018b0cd43543dc94c921341b64b5ec upstream.

    Commit c7f486567c1d0acd2e4166c47069835b9f75e77b
    (PCI PM: PCIe PME root port service driver) causes the native PCIe
    PME signaling to be used by default, if the BIOS allows the kernel to
    control the standard configuration registers of PCIe root ports.
    However, the native PCIe PME is coupled to the native PCIe hotplug
    and calling pcie_pme_acpi_setup() makes some BIOSes expect that
    the native PCIe hotplug will be used as well. That, in turn, causes
    problems to appear on systems where the PCIe hotplug driver is not
    loaded. The usual symptom, as reported by Jaroslav Kameník and
    others, is that the ACPI GPE associated with PCIe hotplug keeps
    firing continuously causing kacpid to take substantial percentage
    of CPU time.

    To work around this issue, change the default so that the native
    PCIe PME signaling is only used if directly requested with the help
    of the pcie_pme= command line switch.

    Fixes , which is
    a listed regression from 2.6.33.

    Signed-off-by: Rafael J. Wysocki <>
    Reported-by: Jaroslav Kameník <>
    Tested-by: Antoni Grzymala <>
    Signed-off-by: Jesse Barnes <>
    Signed-off-by: Greg Kroah-Hartman <>

    Documentation/kernel-parameters.txt | 4 +++-
    drivers/pci/pcie/pme/pcie_pme.c | 19 +++++++++++++------
    2 files changed, 16 insertions(+), 7 deletions(-)

    --- a/Documentation/kernel-parameters.txt
    +++ b/Documentation/kernel-parameters.txt
    @@ -2013,7 +2013,9 @@ and is between 256 and 4096 characters.
    WARNING: Forcing ASPM on may cause system lockups.

    pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
    - off Do not use native PCIe PME signaling.
    + Format: {auto|force}[,nomsi]
    + auto Use native PCIe PME signaling if the BIOS allows the
    + kernel to control PCIe config registers of root ports.
    force Use native PCIe PME signaling even if the BIOS refuses
    to allow the kernel to control the relevant PCIe config
    --- a/drivers/pci/pcie/pme/pcie_pme.c
    +++ b/drivers/pci/pcie/pme/pcie_pme.c
    @@ -34,7 +34,7 @@
    * being registered. Consequently, the interrupt-based PCIe PME signaling will
    * not be used by any PCIe root ports in that case.
    -static bool pcie_pme_disabled;
    +static bool pcie_pme_disabled = true;

    * The PCI Express Base Specification 2.0, Section 6.1.8, states the following:
    @@ -64,12 +64,19 @@ bool pcie_pme_msi_disabled;

    static int __init pcie_pme_setup(char *str)
    - if (!strcmp(str, "off"))
    - pcie_pme_disabled = true;
    - else if (!strcmp(str, "force"))
    + if (!strncmp(str, "auto", 4))
    + pcie_pme_disabled = false;
    + else if (!strncmp(str, "force", 5))
    pcie_pme_force_enable = true;
    - else if (!strcmp(str, "nomsi"))
    - pcie_pme_msi_disabled = true;
    + str = strchr(str, ',');
    + if (str) {
    + str++;
    + str += strspn(str, " \t");
    + if (*str && !strcmp(str, "nomsi"))
    + pcie_pme_msi_disabled = true;
    + }
    return 1;
    __setup("pcie_pme=", pcie_pme_setup);

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