Hi,
I am debugging an issue for a USB device (usb wifi dongle from TP-LINK
TL-WN321G which is using Ralink RT73 chipset). I am using it on an
embedded board running Linux 2.6.30 on ARM architecture.
When I configure the USB controller in USB 1.1 speed, my USB device
(i.e. usb wifi dongle) works perfectly fine. But when the USB controller
is configured for USB 2.0, the device stops working *after some time*
when doing large data transfer at high speed.
The system becomes non-responsive. I could capture the USB packets
(using analyzer) between controller and device and found that there was
*continuous* PING - NAK token exchanges were happening. I could
re-confirm this scenario by putting some debug prints in controller
driver. From this observation, I assumed that it may happen that device
is not able to release the buffers and because of that its sending NAK
to each incoming PING request.
When I reduced the number of PINGs sent out by USB controller driver,
the device was working fine. Currently I am skipping every alternate
PING token from controller driver, but it is hitting network performance
badly.
From my experiments, I found that USB host controller is working
perfectly fine with mass storage devices.
ALSO USB WiFi dongle is working fine with X86 platform (Desktop PC which
has intel usb hcd). I found that USB wifi dongle has the same bulk
in/out endpoints as of mass storage devices (i.e. no interrupt endpoints
are present in dongle).
I am not sure in which direction I should debug further. Any inputs in
same regard will be helpful.
--
Thanks,
Viral Mehta,
Embedded Software Engineer,
Tel. No. 91 79 26563705, Ext. 423
www.einfochips.com <http://www.einfochips.com>
Prepare and Prevent rather than Repair and Repent
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