Hi Alan, All this info is second- or third-hand, so please excuse the extremely vague bug report. A new Intel Atom system (Baytrail) comes with both an xHCI host and an EHCI host, but the BIOS has an "EHCI only" option that hides the xHCI host PCI device from the operating system. It appears that when the BIOS is in this mode, the EHCI PCI interrupt is disabled, and the host simply doesn't work. Jamie and Gaggery have more details about the system and the exact failure mode. They can provide dmesg as well as a PCI register space dump, if necessary. (Jamie and Gaggery, please note, a publicly archived mailing list is Cc'ed.) A customer reports that the following patch fixes the issue: diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c index 3e86bf4371b3..e77566a021ec 100644 --- a/drivers/usb/host/ehci-pci.c +++ b/drivers/usb/host/ehci-pci.c @@ -112,6 +112,9 @@ static int ehci_pci_setup(struct usb_hcd *hcd) case PCI_VENDOR_ID_INTEL: if (pdev->device == PCI_DEVICE_ID_INTEL_CE4100_USB) hcd->has_tt = 1; + /* Baytrail BIOS in EHCI only mode fails to enable interrupts */ + if (pdev->device == 0x0f34) + pci_intx(pdev, 1); break; case PCI_VENDOR_ID_TDI: if (pdev->device == PCI_DEVICE_ID_TDI_EHCI) I looked through the USB PCI initialization code, and I can't find any place where interrupts are enabled, so I assume the PCI core is supposed to enable interrupts? Or is it assumed that the system boots with all PCI device interrupts enabled? In that case, is it a BIOS issue? Sarah Sharp -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
