2018-05-31 11:56 GMT+02:00 Bjørn Mork <bjorn@xxxxxxx>: > Daniele Palmas <dnlplm@xxxxxxxxx> writes: > >> Testing Telit LM940 with ICMP packets > 14552 bytes revealed that >> the modem needs FLAG_SEND_ZLP to properly work, otherwise the cdc >> mbim data interface won't be anymore responsive. >> >> Signed-off-by: Daniele Palmas <dnlplm@xxxxxxxxx> > > Acked-by: Bjørn Mork <bjorn@xxxxxxx> > > Should have thought of this... I noticed your discussion, but couldn't > reproduce the issues myself. This explains why. > > Do you happen to know if the device announces larger buffers than the > driver wants to use, or if this happens with the max sized buffers too? > > You can easily check these values by comparing dwNtbInMaxSize and > dwNtbOutMaxSize (device maximum values) with rx_max and tx_max > (neogtiated values) using e.g > > grep . /sys/class/net/wwan0/cdc_ncm/* > This seems to happen with the max sized buffers according to the output: daniele@L2122:/home/daniele$ grep . /sys/class/net/wwp0s20u6i2/cdc_ncm/* /sys/class/net/wwp0s20u6i2/cdc_ncm/bmNtbFormatsSupported:0x0001 /sys/class/net/wwp0s20u6i2/cdc_ncm/dwNtbInMaxSize:16384 /sys/class/net/wwp0s20u6i2/cdc_ncm/dwNtbOutMaxSize:16384 /sys/class/net/wwp0s20u6i2/cdc_ncm/min_tx_pkt:13312 /sys/class/net/wwp0s20u6i2/cdc_ncm/ndp_to_end:N /sys/class/net/wwp0s20u6i2/cdc_ncm/rx_max:16384 /sys/class/net/wwp0s20u6i2/cdc_ncm/tx_max:16384 /sys/class/net/wwp0s20u6i2/cdc_ncm/tx_timer_usecs:400 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNdpInAlignment:4 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNdpInDivisor:1 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNdpInPayloadRemainder:0 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNdpOutAlignment:4 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNdpOutDivisor:4 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNdpOutPayloadRemainder:0 /sys/class/net/wwp0s20u6i2/cdc_ncm/wNtbOutMaxDatagrams:16 Thanks, Daniele > > It has never been 100% clear to me whether we should send the ZLP by > default if we've negotiated a smaller than max buffer. But the ZLP ought > to be redundant in any case, since the device knows the negotiated > buffer size. So I do believe our current interpretation makes sense. > > Not that it matters. There are obviously more than enough device > implementations violating this requirement to make it completely > pointless. > > > Bjørn -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
