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List:       linux-usb-devel
Subject:    Re: [linux-usb-devel] EHCI & OHCI interrupt weirdness
From:       David Brownell <david-b () pacbell ! net>
Date:       2005-01-19 20:18:54
Message-ID: 200501191218.55204.david-b () pacbell ! net
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On Wednesday 19 January 2005 11:42 am, Jesse Barnes wrote:
> On Wednesday, January 19, 2005 11:20 am, David Brownell wrote:
> > What happens when you load EHCI _only_ ?  Normally loading that driver
> > won't cause any interrupts at all, until some device is connected.
> 
> Yep, that's what happens.  I have a USB 1.1 kbd plugged into the 2.0 port and 
> I don't see any interrupts:
> 
>  67:          0          0          0          0          SN hub  ehci_hcd

Well that seems wrong.  The USB signaling should have woken up
the EHCI driver, causing an IRQ, when that keyboard was plugged in.
(Though that's only _needed_ for now when the port issues RESUME
signaling.)

Specifically a Port Change Detect (PCD) IRQ ... if you build with
CONFIG_USB_DEBUG, then the /sys/class/usb_host/usb1/registers file
should reflect some wierdness.  And the dmesg trace should show
that khubd noticed a device there, and caused it to be handed off
to the (OHCI) companion controller.

- Dave


> > Then there are basically two paths:  (a) it's a full/low speed device,
> > handled by OHCI (or on some cards, UHCI); or (b) it's a high speed device,
> > handled by EHCI.  To test the latter, I suggest you grab a USB 2.0 hub;
> > the slim 4 port ones using Mini-B connectors, just a bit bigger than a
> > credit card, are the most featureful.  (They have Cypress chips that have
> > a transaction translator on each port; which means you can hook up a lot
> > more full and low speed devices downstream.  All controlled by EHCI.)
> 
> Ok, that's worth a try to make sure EHCI is working at all (I suspect it is).
> 
> > Maybe you have issues with IRQ sharing?
> 
> Quite possible since it looks like the EHCI chip shares an IRQ with one of the 
> OHCI chips.  I'll take a look at that.
> 
> Thanks,
> Jesse
> 


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