Hello, On 12/12/2014 07:21 AM, Peter Chen wrote: > On Thu, Dec 11, 2014 at 08:34:45AM -0600, Felipe Balbi wrote: >> Hi, >> >> On Thu, Dec 11, 2014 at 04:08:43PM +0530, Sanchayan Maity wrote: >>> Hello, >>> >>> I am working on a Freescale Cortex-A5 Vybrid Processor. The chip core >>> is clocked at 500MHz and the USB IP core for this is by Chip-idea. I >>> am running a 3.18-rc5 kernel on it and trying to use the USB gadget >>> functionality. To be more specific the CDC ECM class. Currently, I >>> cannot use this properly. If I use just "ping" to check, it works >>> fine, but, after running iperf, even one transaction doesn't complete >>> or completes rarely. Checking the CDC Ether interface with Wireshark >>> shows, TCP Dup Ack messages and checking the USB bus with Wireshark, >>> shows packets with USB Protocol Error -71 at one point and after that >>> packets with USB connection Reset -104 error. If it's of any >>> significance, I have Arch Linux with the 3.18 kernel running on my >>> laptop with which the Vybrid connects. On the host side, the only >>> error dmesg shows is "kevent 12 may have been dropped". I guess this >>> is connected to the "TCP Previous Segment not captured" and "TCP Dup >>> ACK" messages. >>> >>> My script for the gadget configuration is as below: >>> >>> /bin/mount none /mnt -t configfs >>> /bin/mkdir /mnt/usb_gadget/g1 >>> cd /mnt/usb_gadget/g1 >>> /bin/mkdir configs/c.1 >>> /bin/mkdir functions/ecm.0 >>> /bin/mkdir strings/0x409 >>> /bin/mkdir configs/c.1/strings/0x409 >>> echo 0xa4a2 > idProduct >>> echo 0x0525 > idVendor >>> echo Freescale123 > strings/0x409/serialnumber >>> echo Freescale > strings/0x409/manufacturer >>> echo "USB Serial Gadget" > strings/0x409/product >>> echo "Conf 1" > configs/c.1/strings/0x409/configuration >>> echo 200 > configs/c.1/MaxPower >>> ln -s functions/ecm.0 configs/c.1 >>> echo ci_hdrc.0 > UDC >>> /sbin/ifconfig usb0 up >>> /sbin/ifconfig usb0 192.168.1.10 >>> >>> I have debug prints in the udc.c and u_ether.c using pr_debug and >> >> just a little hint, use any of the dev_*() macros next time, they'll >> print the device name which helps figuring out which UDC you're using. >> >> Based on ci_hdrc.0 above, I suppose it's chipidea and Peter Chen >> maintains that one, it really helps adding maintainers to Cc list. >> >>> enable them when required using dynamic debug. Without running iperf, >>> using ping gives me a sequence of prints as below: >>> >>> [ 277.434409] In eth_start_xmit >>> [ 277.434517] In UDC irq >>> [ 277.434553] In usb_gadget_giveback_request >>> [ 277.434567] In tx_complete >>> [ 277.435443] In UDC irq >>> [ 277.435477] In usb_gadget_giveback_request >>> [ 277.435491] In rx_complete >>> [ 277.435517] In rx_submit >>> [ 277.435601] In eth_start_xmit >>> [ 277.436441] In UDC irq >>> [ 277.436465] In usb_gadget_giveback_request >>> [ 277.436478] In rx_complete >>> [ 277.436493] In rx_submit >>> [ 277.436520] In usb_gadget_giveback_request >>> [ 277.436533] In tx_complete >>> [ 278.434865] In eth_start_xmit >>> [ 278.434959] In UDC irq >>> [ 278.434993] In usb_gadget_giveback_request >>> [ 278.435006] In tx_complete >>> [ 278.435881] In UDC irq >>> [ 278.435910] In usb_gadget_giveback_request >>> [ 278.435923] In rx_complete >>> [ 278.435946] In rx_submit >>> >>> After running iperf without debug prints and then enabling before >>> using ping gives me a sequence of prints as below >>> [ 81.989827] In UDC irq >>> [ 81.989871] In usb_gadget_giveback_request >>> [ 81.989886] In rx_complete >>> [ 81.989905] In rx_submit >>> [ 82.989892] In UDC irq >>> [ 82.989951] In usb_gadget_giveback_request >>> [ 82.989967] In rx_complete >>> [ 82.989992] In rx_submit >>> [ 83.990064] In UDC irq >>> [ 83.990126] In usb_gadget_giveback_request >>> [ 83.990142] In rx_complete >>> [ 83.990167] In rx_submit >>> [ 84.990007] In UDC irq >>> [ 84.990049] In usb_gadget_giveback_request >>> [ 84.990064] In rx_complete >>> [ 84.990083] In rx_submit >>> [ 85.990085] In UDC irq >>> [ 85.990147] In usb_gadget_giveback_request >>> [ 85.990163] In rx_complete >>> [ 85.990188] In rx_submit >>> >>> If I force a full speed configuration for this USB client port, I get >>> a slightly more reliable operation where iperf can run for may be half >>> an hour or so or almost an hour before it falls through. Putting in a >>> delay of 100-150 microseconds in eth_start_xmit also improves it like >>> full speed, but, still not reliable. If I run iperf with debug prints >>> enable, this gives similar results to full speed config. After the >>> failure of iperf test, even ping doesn't work. Bringing down this usb0 >>> interface and then up again makes ping work again. I do realize that >>> putting debug prints or delays like this is not the right thing to do, >>> especially in ISR, but, just trying to debug. This is my first time >>> digging in the USB stack. >>> >>> Based on the above, it seems there might a subtle bug or race >>> condition somewhere in the execution call chain which I have not been >>> able to trace yet. Can someone give me some pointers on how I can dig >>> and debug further?. >> > > I just tried latest usb-next with i.mx6 platform, it works ok with > 10 mins iperf bi-direction test. We did think that it is probably an issue seen with Vybrids only. > > I am wronging Vybrid is not fast enough, run top to see if iperf > occupies too much (>95%) cpu utilization, if it is, run perf top > (or similar perf tool) to see which function affects most, > from my experiences, CONFIG_SMP affects UP platform's performance, > try to disable it. Yes, probably one of the slowest SOC's for USB IP around may be. CPU utilisation is not high during iperf. CONFIG_SMP is not set. > >> yeah, I'd start pointing fingers at chipidea. But just to make sure, can >> you try the same thing with dummy_hcd ? dummy_hcd is a SW-only host and >> peripheral "controller" pair tied together. If that one works, you >> definitely have a bug with chipidea. >> >> If you want to debug chipidea like that, I'd strongly suggest using >> either tracepoints (which would have to be added to chipidea; but hey, >> desirable patch - see drivers/usb/dwc3/trace.h for reference) or just >> use plain old trace_printk(). >> >> Then setup a huge trace buffer (I usually go for 20MiB or more) and >> reproduce the failure; read trace, add more traces, try again, until you >> find out where the problem lies. >> >> good luck, and please send patches if you manage to solve the problem >> :-) >> >> -- >> balbi > > > -Regards Sanchayan -- 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
