Re: Embedded Linux USB 3.0 OTG - xhci-hcd

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Ok, recent kernel, same results. Dmesgs to follow - need to enable
verbose xhci (and such) messages. (Just went to DST here (Jalisco, MX)
which always messes me about).
David

On sáb, 2014-04-05 at 20:52 -0400, Alan Stern wrote:
> On Sat, 5 Apr 2014, David Kochendorfer wrote:
> 
> > Hi,
> > 
> > I'm having a problem with my Android phone USB 3.0 port: when I attach a
> > 3.0 storage gadget/accessory (Extreme USB 3.0 - 64GB, formated as ext4),
> > I do see an entry in /dev/block/platform/xhci-hcd, but when a I mount
> > the device and copy a relatively large file (~2GB) to it, I see real
> > times of 55-63 seconds. And when I look at the associated dmesgs, it
> > appears that xhci-hcd is running USB2.
> > 
> > The phone SOC - is an MSM-8974 with a 3.0 hub, and my kernel is
> > 3.4.78-g8126c7a.
> > 
> > I'm relatively knowledgeable about linux drivers, in general, and with
> > the USB 3.0 spec, but not the USB driver and am having trouble tracking
> > down what's going on.
> > 
> > Can someone please point me to a document, that details the functional
> > flow of the usb driver from cable/device change through enumeration an
> > xhci-hcd initialization, if such a thing exists?
> 
> It doesn't.  :-(
> 
> > Also, is there a way to force the hub to USB3?
> 
> Isn't the embedded hub already on the USB-3 bus?  If it isn't using 
> that bus, there's no way to force it.
> 
> >  I'm not looking for a
> > "generic - approved" linux driver solution (i.e. I'm not trying to
> > generate a patch to submit, I just want to get the transfers sped up in
> > my kernel for this particular case).
> 
> The choice of which bus to use, USB-2 or USB-3, is made by the device 
> when it connects.  The kernel can't tell a device to use the USB-3 
> bus.
> 
> Maybe if you post your dmesg log, some of the xHCI maintainers will 
> have useful suggestions.  I can tell you right away what the first 
> suggestion will be, though: Use a more up-to-date kernel.  3.4 is 
> pretty old, considering the rapid rate of development of xhci-hcd.
> 
> Alan Stern
> 

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