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SubjectRe: [PATCH] USB: ehci-pci: USB host controller support for Intel Quark X1000
On Tue, Jun 24, 2014 at 08:51:43AM -0700, Chen, Alvin wrote:
> From: Bryan O'Donoghue <bryan.odonoghue@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.odonoghue@intel.com>
> Signed-off-by: Alvin (Weike) Chen <alvin.chen@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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