From: Bjørn Mork <bjorn@xxxxxxx> commit c086e7096170390594c425114d98172bc9aceb8a upstream. Several Lenovo users have reported problems with their Sierra Wireless EM7455 modem. The driver has loaded successfully and the MBIM management channel has appeared to work, including establishing a connection to the mobile network. But no frames have been received over the data interface. The problem affects all EM7455 and MC7455, and is assumed to affect other modems based on the same Qualcomm chipset and baseband firmware. Testing narrowed the problem down to what seems to be a firmware timing bug during initialization. Adding a short sleep while probing is sufficient to make the problem disappear. Experiments have shown that 1-2 ms is too little to have any effect, while 10-20 ms is enough to reliably succeed. Reported-by: Stefan Armbruster <ml001@xxxxxxxxxxxxxxxx> Reported-by: Ralph Plawetzki <ralph@xxxxxxxxxxxx> Reported-by: Andreas Fett <andreas.fett@xxxxxxxxxxx> Reported-by: Rasmus Lerdorf <rasmus@xxxxxxxxxxx> Reported-by: Samo Ratnik <samo.ratnik@xxxxxxxxx> Reported-and-tested-by: Aleksander Morgado <aleksander@xxxxxxxxxxxxx> Signed-off-by: Bjørn Mork <bjorn@xxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Willy Tarreau <w@xxxxxx> --- drivers/net/usb/cdc_ncm.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index 6ee9665..a580241 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -477,6 +477,13 @@ advance: if (cdc_ncm_setup(ctx)) goto error2; + /* Some firmwares need a pause here or they will silently fail + * to set up the interface properly. This value was decided + * empirically on a Sierra Wireless MC7455 running 02.08.02.00 + * firmware. + */ + usleep_range(10000, 20000); + /* configure data interface */ temp = usb_set_interface(dev->udev, iface_no, data_altsetting); if (temp) -- 2.8.0.rc2.1.gbe9624a -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html