Hi, Sorry for the delayed response, I was traveling during the last week too. On Monday, September 12, 2011, Sarah Sharp wrote: > Hi Rafael, > > As I mentioned at LPC, I have a USB host controller that is failing to > wakeup from D3 when a new USB device is connected to an external hub. > The system is in S0 at this point. > > You mentioned that there were two ways for hardware to generate PMEs: > either through the standard PCI interrupt process, or via an ACPI SCI > call. > > I think the hardware engineers want Linux to set up the PCI device to > generate PMEs via an SCI call, but I'm not sure if Linux is. I've tried > turning on ACPI debugging (with level and layers both set to 0xffffffff > so I can see all debugging), and I don't see any output at all from ACPI > functions like acpi_ev_sci_xrupt_handler when the host controller comes > out of D3. (It does come out of D3 if I plug in the device within 10 > seconds of PCI suspend, for whatever reason.) > > Is there a way to tell if SCI is being used by a PCI device to generate > PMEs? Yes, there is. First, if the native PCIe PME is used (which means SCI isn't), there will be entries like these in /proc/interrupts: 40: 0 0 PCI-MSI-edge PCIe PME 41: 0 0 PCI-MSI-edge PCIe PME 42: 0 0 PCI-MSI-edge PCIe PME If they are not present, it means that the kernel is _trying_ to use SCI for PME signaling. In that case, you can check if the number of ACPI interrupts in /proc/interrupts is increasing when you try to trigger the events. In that case you can use the files under /sys/firmware/acpi/interrupts/ to see what GPEs are activated by the wakeup events. > You also mentioned that Linux has to choose whether to use standard > interrupts or an SCI to generate PMEs. You said Linux asks the BIOS if > the hardware can use interrupts to generate PMEs, and it always uses > interrupt-based PME generation if the BIOS says yes. That's correct. > Do you know where that code is? drivers/acpi/pci_root.c:acpi_pci_root_add() > I'd like to see how the BIOS responds to that call, and perhaps get the > BIOS guys to fix their response if the hardware is supposed to only use > SCIs to generate PMEs. The BIOS should respond by clearing bit 2 (PCIe PME) of the control field returned from _OSC() invoked for the PCIe Root Complex (meaning that the kernel is not granted control of the native PCIe feature). Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
