Hello, I faced the deaf wwan0 problem with a Huawei E3372h-153.
I'm not using ModemManager but OpenWrt CC-rc2, with Linux 3.18.14. I've enabled the debug port of the android running in the stick. (Yes, it's running android but without dalvik, don't ask me why since it isn't even tethering in the standard android way... The embedded linux can't even see the modem interface via ifconfig, it's just a relay between the vxworks that handles the modem and the usb port. Mah.) To enable the debug port, just search on the 'net and you will easily find the commands. You can brick the modem permanently if you play too much with it; so I'm not going to write the commands here, since I don't want any responsibility if you happen to break your internet key this way. Be careful! ;) Anyway, I've seen that the android dmesg log was full of errors, one line per packet sent from the host to the modem: [002173183ms] ====ERROR:gnet_copy_skb skb->len=526 should be greater than len=342 + offset=184==== [002173935ms] ====ERROR:gnet_copy_skb skb->len=226 should be greater than len=42 + offset=184==== [002176186ms] ====ERROR:gnet_copy_skb skb->len=526 should be greater than len=342 + offset=184==== [002176207ms] ====ERROR:gnet_copy_skb skb->len=226 should be greater than len=42 + offset=184==== [002177205ms] ====ERROR:gnet_copy_skb skb->len=226 should be greater than len=42 + offset=184==== [002178205ms] ====ERROR:gnet_copy_skb skb->len=226 should be greater than len=42 + offset=184==== [002179187ms] ====ERROR:gnet_copy_skb skb->len=526 should be greater than len=342 + offset=184==== After testing many things, I've found the "magic" settings that do work: echo 6000 > /sys/class/net/wwan0/cdc_ncm/tx_max echo 0 > /sys/class/net/wwan0/cdc_ncm/min_tx_pkt After issuing these commands, the interface works fine! (Or at least it seems for now...) Of course, I think that it's way far from perfect, but it's a starting point for debugging at least. I've seen that setting tx_max to 1698 (the minimum) only allows packets up to 1496 bytes to work (ping -s 1468). If I increase the tx_max, the limit changes of course, and 1500-byte packets get sent correctly. But if the tx_max is too big, like with the default of 16384, a lot of delay is introduced. It seems that a buffer needs to get full before the packets are sent to the modem and then out to the internet... (I've checked with tcpdump on the remote host that the modem will not send out packets before this hypotethical buffer gets full, then they are sent all together.) The number 6000 for tx_max seems to be a fair compromise between low delay (it's like with 1698) and being able to send big packets in a burst (I've tested with fragmented ping up to -s 30000, and also wget of a big file works great). If you need some more testing, definitely let me know! (By the way, just a note since it helped me with OpenWrt and might help you too: in case you don't get AT^NDISDUP to connect, it's because this stick seems not to want the APN name specified there. Instead, just set it with AT+CGDCONT=1,"IP","apn" and then send AT^NDISDUP=1,1 to connect. To disconnect, send AT^NDISDUP=1,0 .) Best regards, Vittorio G _______________________________________________ ModemManager-devel mailing list ModemManager-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/modemmanager-devel
