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authorBjørn Mork <bjorn@mork.no>2016-07-03 22:24:50 +0200
committerSasha Levin <alexander.levin@verizon.com>2016-08-19 23:08:38 -0400
commit5c4642407d9c696dadef7fba557244c2d69d96dd (patch)
treea0ae3058f7c04b913f86a67a84a66f9f515b75ba /drivers/net
parent28a6d048eb841a6bca10558a6c9e30ec5ca2b1af (diff)
cdc_ncm: workaround for EM7455 "silent" data interface
[ Upstream commit c086e7096170390594c425114d98172bc9aceb8a ] 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@armbruster-it.de> Reported-by: Ralph Plawetzki <ralph@purejava.org> Reported-by: Andreas Fett <andreas.fett@secunet.com> Reported-by: Rasmus Lerdorf <rasmus@lerdorf.com> Reported-by: Samo Ratnik <samo.ratnik@gmail.com> Reported-and-tested-by: Aleksander Morgado <aleksander@aleksander.es> Signed-off-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Diffstat (limited to 'drivers/net')
-rw-r--r--drivers/net/usb/cdc_ncm.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 5db25e46a962..5dbc1744eba5 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -858,6 +858,13 @@ advance:
if (cdc_ncm_init(dev))
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) {