linux-kernel - RE: [PATCH] USB: ehci-pci: USB host controller support for Intel Quark X1000

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Date:	Wed, 25 Jun 2014 09:24:36 +0000
From:	"Chen, Alvin" <alvin.chen@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Alan Stern <stern@...land.harvard.edu>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Ong, Boon Leong" <boon.leong.ong@...el.com>
Subject: RE: [PATCH] USB: ehci-pci: USB host controller support for Intel
 Quark X1000

See my comments below:

> -----Original Message-----
> From: Greg Kroah-Hartman [mailto:gregkh@...uxfoundation.org]
> Sent: Tuesday, June 24, 2014 9:25 PM
> To: Chen, Alvin
> Cc: Alan Stern; linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org; Ong,
> Boon Leong
> Subject: Re: [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@...el.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@...el.com>
> > Signed-off-by: Alvin (Weike) Chen <alvin.chen@...el.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?
> 
Actually, 'unlikely' is not necessary, I will remove it in PATCH v2.

> thanks,
> 
> greg k-h
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