On Tue, Jun 24, 2014 at 08:51:43AM -0700, Chen, Alvin wrote:
> From: Bryan O'Donoghue <bryan.odonog...@intel.com>
> 
> This patch is to enable USB host controller for Intel Quark X1000. Add pci 
> quirks
> to adjust the packet buffer in/out threshold value, and ensure EHCI packet 
> buffer
> i/o threshold value is reconfigured to half.
> 
> Signed-off-by: Bryan O'Donoghue <bryan.odonog...@intel.com>
> Signed-off-by: Alvin (Weike) Chen <alvin.c...@intel.com>
> ---
>  drivers/usb/host/ehci-pci.c   |    4 ++++
>  drivers/usb/host/pci-quirks.c |   42 
> +++++++++++++++++++++++++++++++++++++++++
>  drivers/usb/host/pci-quirks.h |    2 ++
>  3 files changed, 48 insertions(+)
> 
> diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
> index 3e86bf4..33cfa23 100644
> --- a/drivers/usb/host/ehci-pci.c
> +++ b/drivers/usb/host/ehci-pci.c
> @@ -50,6 +50,10 @@ static int ehci_pci_reinit(struct ehci_hcd *ehci, struct 
> pci_dev *pdev)
>       if (!retval)
>               ehci_dbg(ehci, "MWI active\n");
>  
> +     /* Reset the threshold limit */
> +     if(unlikely(usb_is_intel_qrk(pdev)))

Why unlikely()?  Have you measured a speed difference here?  And this is
a _very_ slow path, what does that speed difference you measured help
with?

thanks,

greg k-h
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