On Mon, Jan 15, 2018 at 5:20 PM, Yazen Ghannam <Yazen.Ghannam@xxxxxxx> wrote: > From: Yazen Ghannam <yazen.ghannam@xxxxxxx> > > Currently, aer_service_init() checks if AER is available and that > Firmware First handling is not enabled. The _OSC request for AER is not > taken into account when deciding to enable AER in Linux. > > From ACPI 6.2 Section 6.2.11.3, "If any bits in the Control Field are > returned cleared (masked to zero) by the _OSC control method, the > respective feature is designated unsupported by the platform and must > not be enabled by the OS." > > The OS and the Platform should agree that the OS can have control of AER > otherwise we should disable AER in the OS. > > Mark AER as disabled if the _OSC request was not made or accepted. > > This covers two cases where the OS and Platform disagree: > 1) The OS requests AER control and Platform denies the request. > 2) The OS does not request AER control but the Platform returns the AER > control bit set, possibly due to a Firmware bug. > > The _OSC control for AER is not requested when APEI Firmware First is > used, so the same condition applies from case 2 above. > > Remove redundant check for aer_acpi_firmware_first() when calling > aer_service_init(), since this check is already included when checking > the _OSC control. > > Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx> Bjorn, what do you think? > --- > Link: > https://lkml.kernel.org/r/20180111150316.19951-1-Yazen.Ghannam@xxxxxxx > > v1->v2: > * Expand commit message. > * Add Spec reference to commit message. > * Fix spelling error in commit message. > * Add comment for 3-way bitwise AND. > > drivers/acpi/pci_root.c | 7 +++++++ > drivers/pci/pcie/aer/aerdrv.c | 2 +- > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c > index 6fc204a52493..ab0192fd24c7 100644 > --- a/drivers/acpi/pci_root.c > +++ b/drivers/acpi/pci_root.c > @@ -512,6 +512,13 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm) > */ > *no_aspm = 1; > } > + > + /* > + * We can use a 3-way bitwise AND to check that the AER control bit is > + * both requested by the OS and granted by the Platform. > + */ > + if (!(requested & control & OSC_PCI_EXPRESS_AER_CONTROL)) > + pci_no_aer(); > } > > static int acpi_pci_root_add(struct acpi_device *device, > diff --git a/drivers/pci/pcie/aer/aerdrv.c b/drivers/pci/pcie/aer/aerdrv.c > index 6ff5f5b4f5e6..39bb059777d0 100644 > --- a/drivers/pci/pcie/aer/aerdrv.c > +++ b/drivers/pci/pcie/aer/aerdrv.c > @@ -374,7 +374,7 @@ static void aer_error_resume(struct pci_dev *dev) > */ > static int __init aer_service_init(void) > { > - if (!pci_aer_available() || aer_acpi_firmware_first()) > + if (!pci_aer_available()) > return -ENXIO; > return pcie_port_service_register(&aerdriver); > } > --
