On 06.01.2012 19:03, Alan Stern wrote:
> On Fri, 6 Jan 2012, Matthias Fuchs wrote:
>
>> For my eyes it does not really look like a general USB issue.
>> It looks like a problem with the Freescale EHCI implementation that is
>> influenced by high interrupt or internal bus load caused by the flood ping.
>
> Indeed, it might be a problem with the built-in Transaction Translator.
> That would explain why it affect full-speed devices.
>
> However, I would expect the resetting the controller hardware (which
> happens when you reload the ehci-fsl driver) would fix any such issues.
> It's hard to imagine how a problem could survive a reset like that.
I did the tests again. When the error occured I reloaded the ehci-hcd driver
and reconnected the device. It ends up with some kernel messages
that come up time after time:
usb 1-1: new full-speed USB device number 2 using fsl-ehci
usb 1-1: device descriptor read/64, error -110
usb 1-1: device descriptor read/64, error -110
usb 1-1: new full-speed USB device number 3 using fsl-ehci
usb 1-1: device descriptor read/64, error -110
usb 1-1: device descriptor read/64, error -110
usb 1-1: new full-speed USB device number 4 using fsl-ehci
usb 1-1: device not accepting address 4, error -110
usb 1-1: new full-speed USB device number 5 using fsl-ehci
usb 1-1: device not accepting address 5, error -110
hub 1-0:1.0: unable to enumerate USB device on port 1
A recommondation from freescale was to check the TXFILLTUNING register settings
("Initialization of this registers can produce problem if full-speed device is
used").
So I tried various values in the TXFILLTUNING register (I added this
code to ehci_reset()). Finally I disabled USB streaming mode in the USBMODE
register (set bit USBMODE_SDIS - btw., it should be defined as "1 << 4" in
ehci_def.h at least for the MPC5121).
All this does not fix the problem or even have an impact.
This is my stripped down version of the test:
on the MPC5121 unit I do nothing but:
$~ stty -F /dev/ttyUSB0 -echo -crtscts -cstopb
$~ stty -F /dev/ttyUSB0 115200
$~ while true; do \
read LINE < /dev/ttyUSB0 \
echo $LINE > /dev/ttyUSB0 \
done
The other side looks like this:
$~ while true; do \
echo "_THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG 1234567890#" >
/dev/ttyS0 \
done
and also I start a flood ping against the MPC5121 unit (.. to speed things up).
Can anybody with a MPC5121 board try to reproduce this?
Matthias
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