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Re: Hi-Speed USB controller and au1500

Subject: Re: Hi-Speed USB controller and au1500
From: (Bruno Randolf)
Date: Sat, 23 Oct 2004 16:38:15 +0200
Cc: "'Eric DeVolder'" <>
In-reply-to: <CECB0B0453C6D511BEB800104B70FA47B4A025@STARBASE>
Organization: 4G Systems
Original-recipient: rfc822;
References: <CECB0B0453C6D511BEB800104B70FA47B4A025@STARBASE>
User-agent: KMail/1.7
maybe not everything ist fixed in AD stepping... we have observed that on our 
Au1500 AD board the internal USB host only works when we set 

without CONFIG_NONCOHERENT_IO=y we get crashes when the used usb bandwidth 
gets higher. for example with an USB ethernet adapter: ping works but real 
traffic makes the kernel crash. usb-storage does not work at all.

can you confirm this?

would it be possible to use CONFIG_NONCOHERENT_IO=y only for USB, and not PCI? 
we have PCI cards (prism54) which only work without CONFIG_NONCOHERENT_IO, so 
at the moment we can either have USB host or prism54 based PCI cards...


On Friday 22 October 2004 16:15, Yates, John wrote:
> Thank you. This indeed works.
> The CONFIG_NONCOHERENT_IO option is set by default in when
> one selects the db1500 board (among others). Does anyone have
> recommendations as to how to modify to give others the
> option of disabling this default behavior?
> Possible places could be:
> 1. Add an override defaults sub-menu for the boards that support disabling
> 2. Add a CONFIG_NONCOHERENT_IO item to the bottom of "Machine Selection"
> menu. (There is already a "High Memory Support" option at the bottom of the
> "machine Selection" menu.)
> 3. Add a CONFIG_NONCOHERENT_IO item to the "Override CPU options" sub-menu
> (in the "CPU Selection" menu).
> 4....
> Thanks, John
> -----Original Message-----
> From: Eric DeVolder []
> Sent: Monday, October 18, 2004 12:28 PM
> To: Yates, John
> Subject: Re: Hi-Speed USB controller and au1500
> I'm guessing that CONFIG_NONCOHERENT_IO is set which means that the
> buffers used by USB are non-cached, and so the LL/SC combinations
> performed by the USB stack to the structs in this non-cached area will
> always fail. (Examine the MIPS LL/SC...only works to cached spaces...)
> Depending upon which version of the Au1500 you have,
> CONFIG_NONCOHERENT_IO was necessary due to coherency bugs. I believe
> everything should be fixed with Au1500 AD so that CONFIG_NONCOHERENT_IO
> isn't needed....
> Eric
> Yates, John wrote:
> >Hello all,
> >
> >I am having a problem using a PCI USB 2.0 Hi-Speed controller (EHCI) with
> >the dbau1500 eval kit with kernel 2.4.26. I have traced the problem down
> > to a call to atomic_add() (in include/asm-mips/atomic.h) that uses
> > assembly to access ll/sc registers of the mips architecture.  If I
> > override CPU options and disable ll/sc when configuring the kernel, 
> > everything works fine. However this causes the atomic_add() to use
> >local_irq_save()/local_irq_restore().  I am assuming this will cause quite
> a
> >performance hit since atomic_add() gets called all over the place.  I
> should
> >include that the ll/sc version of atomic_add() seems to work fine until
> > the call from the usb infrastructure.
> >
> >Below is a code trail that leads to the call to atomic_add():
> >
> >
> >hub.c:   usb_hub_port_connect_change()
> >usb.c:    usb_set_address()
> >usb.c:    usb_control_msg()
> >usb.c:    usb_internal_control_msg()
> >usb.c:    usb_start_wait_urb()
> >usb.c:    usb_submit_urb()
> >usb.c:    submit_urb()
> >hcd.c:    hcd_submit_urb()
> >host/ehci-hcd.c:   ehci_urb_enqueue()  (urb_enqueue
> >function ptr)
> >host/ehci-q.c:   submit_async()
> >host/ehci-q.c:   qh_append_tds()
> >host/ehci-mem.c:   qh_get()
> >atomic.h   atomic_inc()
> >atomic.h   #define atomic_inc(v) atomic_add(1,(v)) <-
> >uses ll/sc
> >
> >To reproduce my results:
> >
> >Plug in a Hi-Speed USB 2.0 controller into your pci slot and boot with a
> usb
> >ehci enabled  kernel. Be sure to disable the non-pci usb host that is
> >built-in to the au1500 when building the  kernel. (I have tried two
> >controllers (NEC and ALi) with identical results.)
> >
> >Plug a Hi-Speed device (thumb drive or external HD) into the controller.
> >(system stops responding here)
> >
> >Low/Full speed devices work without a problem because they use the ohci or
> >uhci drivers.
> >
> >
> >Any help or direction will be greatly appreciated.
> >
> >John

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