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    SubjectRe: [RFC PATCH v2] xhci: Prevent runtime pm from autosuspending during initialization
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    On Fri, Feb 28, 2014 at 1:57 PM, Greg KH <greg@kroah.com> wrote:
    > On Fri, Feb 28, 2014 at 12:41:31PM -0800, Dan Williams wrote:
    >> On Fri, Feb 28, 2014 at 12:32 PM, Sarah Sharp
    >> <sarah.a.sharp@linux.intel.com> wrote:
    >> > On Mon, Feb 24, 2014 at 12:44:46PM -0500, Alan Stern wrote:
    >> >> On Mon, 24 Feb 2014, Mathias Nyman wrote:
    >> >>
    >> >> > xHCI driver has its own pci probe function that will call usb_hcd_pci_probe
    >> >> > to register its usb-2 bus, and then continue to manually register the
    >> >> > usb-3 bus. usb_hcd_pci_probe does a pm_runtime_put_noidle at the end and
    >> >> > might thus trigger a runtime suspend before the usb-3 bus is ready.
    >> >> >
    >> >> > Prevent the runtime suspend by increasing the usage count in the
    >> >> > beginning of xhci_pci_probe, and decrease it once the usb-3 bus is
    >> >> > ready.
    >> >> >
    >> >> > xhci-platform driver is not using usb_hcd_pci_probe to set up
    >> >> > busses and should not need to have it's usage count increased during probe.
    >> >> >
    >> >> > Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
    >> >> > ---
    >> >> > drivers/usb/host/xhci-pci.c | 11 ++++++++++-
    >> >> > 1 file changed, 10 insertions(+), 1 deletion(-)
    >> >> >
    >> >> > diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
    >> >> > index 04f986d..ea7158b 100644
    >> >> > --- a/drivers/usb/host/xhci-pci.c
    >> >> > +++ b/drivers/usb/host/xhci-pci.c
    >> >> > @@ -190,6 +190,10 @@ static int xhci_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
    >> >> > struct usb_hcd *hcd;
    >> >> >
    >> >> > driver = (struct hc_driver *)id->driver_data;
    >> >> > +
    >> >> > + /* Prevent USB-2 roothub runtime suspend until USB-3 is initialized. */
    >> >> > + pm_runtime_get_noresume(&dev->dev);
    >> >>
    >> >> Strictly speaking, this prevents the _controller_ from going into
    >> >> runtime suspend -- not the root hub.
    >> >
    >> > Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
    >>
    >> Pardon the nitpick, but this is an acked-by if Mathias is submitting.
    >
    > No, it's a "chain of signed-off-by's" and this is allowed just fine (it
    > used to be the default-thing before we came up with the "acked-by"
    > line...)

    Ok. jejb picked on me about it once, but I'm more than willing to drop
    this off my list of things to nitpick.


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