From: Rafael J. Wysocki <rjw@xxxxxxx> 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 https://bugzilla.kernel.org/show_bug.cgi?id=15924 , which is a listed regression from 2.6.33. Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx> Reported-by: Jaroslav Kameník <jaroslav@xxxxxxxxxx> Tested-by: Antoni Grzymala <antekgrzymala@xxxxxxxxx> --- Documentation/kernel-parameters.txt | 4 +++- drivers/pci/pcie/pme/pcie_pme.c | 19 +++++++++++++------ 2 files changed, 16 insertions(+), 7 deletions(-) Index: linux-2.6/drivers/pci/pcie/pme/pcie_pme.c =================================================================== --- linux-2.6.orig/drivers/pci/pcie/pme/pcie_pme.c +++ linux-2.6/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); Index: linux-2.6/Documentation/kernel-parameters.txt =================================================================== --- linux-2.6.orig/Documentation/kernel-parameters.txt +++ linux-2.6/Documentation/kernel-parameters.txt @@ -2048,7 +2048,9 @@ 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 registers. -- 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
