Am 13.08.2013 10:09, schrieb Oleksij Rempel:
If usb auto suspend is enabled or system run in to suspend/resume
cycle ath9k-htc adapter will stop to response. It is reproducible on xhci HCs.
Host part of problem:
XHCI do timing calculation based on Transfer Type and bInterval,
immediately after device was detected. Ath9k-htc try to overwrite
this parameters on module probe and some changes in FW,
since we do not initiate usb reset from the driver this changes
are not took to account. So, before any kind of suspend or reset,
host controller will operate with old parameters. Only after suspend/resume
and if interface id stay unchanged, new parameters will by applied. Host
will send bulk data with no intervals (?), which will cause
overflow on FIFO of EP4.
Firmware part of problem:
By default, ath9k-htc adapters configured with EP3 and EP4
as interrupt endpoints. Current firmware will try to overwrite
ConfigDescriptor to make EP3 and EP4 bulk. FIFO for this endpoints
stay not reconfigured, so under the hood it is still Int EP.
After some digging in the code, i see that converting EP3 and EP4 to
bulk was a bug. This endpoints can't handle more then 64bytes, and
normally if we would provide it as usb descriptor, we would got warned.
See this code:
drivers/usb/core/config.c
/*
* Some buggy high speed devices have bulk endpoints using
* maxpacket sizes other than 512. High speed HCDs may not
* be able to handle that particular bug, so let's warn...
*/
if (to_usb_device(ddev)->speed == USB_SPEED_HIGH
&& usb_endpoint_xfer_bulk(d)) {
unsigned maxp;
maxp = usb_endpoint_maxp(&endpoint->desc) & 0x07ff;
if (maxp != 512)
dev_warn(ddev, "config %d interface %d
altsetting %d "
"bulk endpoint 0x%X has invalid
maxpacket %d\n",
cfgno, inum, asnum, d->bEndpointAddress,
maxp);
}
--
Regards,
Oleksij
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