From: Bjørn Mork <bj...@mork.no>

[ Upstream commit 245d21190aec547c0de64f70c0e6de871c185a24 ]

It has been reported that the dummy byte we add to avoid
ZLPs can be forwarded by the modem to the PGW/GGSN, and that
some operators will drop the connection if this happens.

In theory, QMI devices are based on CDC ECM and should as such
both support ZLPs and silently ignore the dummy byte.  The latter
assumption failed.  Let's test out the first.

Signed-off-by: Bjørn Mork <bj...@mork.no>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 drivers/net/usb/qmi_wwan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
index e1e5e8438457..cdf00102fecb 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -531,7 +531,7 @@ static int qmi_wwan_resume(struct usb_interface *intf)
 
 static const struct driver_info        qmi_wwan_info = {
        .description    = "WWAN/QMI device",
-       .flags          = FLAG_WWAN,
+       .flags          = FLAG_WWAN | FLAG_SEND_ZLP,
        .bind           = qmi_wwan_bind,
        .unbind         = qmi_wwan_unbind,
        .manage_power   = qmi_wwan_manage_power,
@@ -540,7 +540,7 @@ static const struct driver_info     qmi_wwan_info = {
 
 static const struct driver_info        qmi_wwan_info_quirk_dtr = {
        .description    = "WWAN/QMI device",
-       .flags          = FLAG_WWAN,
+       .flags          = FLAG_WWAN | FLAG_SEND_ZLP,
        .bind           = qmi_wwan_bind,
        .unbind         = qmi_wwan_unbind,
        .manage_power   = qmi_wwan_manage_power,
-- 
2.14.1

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