| From foo@baz Thu Jul 14 07:36:31 JST 2016 |
| From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@mork.no> |
| Date: Sun, 3 Jul 2016 22:24:50 +0200 |
| Subject: cdc_ncm: workaround for EM7455 "silent" data interface |
| MIME-Version: 1.0 |
| Content-Type: text/plain; charset=UTF-8 |
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| |
| From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@mork.no> |
| |
| [ 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: BjΓΈrn Mork <bjorn@mork.no> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/net/usb/cdc_ncm.c | 7 +++++++ |
| 1 file changed, 7 insertions(+) |
| |
| --- a/drivers/net/usb/cdc_ncm.c |
| +++ b/drivers/net/usb/cdc_ncm.c |
| @@ -809,6 +809,13 @@ int cdc_ncm_bind_common(struct usbnet *d |
| 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) { |
