Am I understanding ehci correctly here? It looks like we only get an interrupt every 8ms even though the isochronous period is 1ms. That's because we can schedule 8 isochronous transactions at a time, meaning the host controller hardware takes over for 8 milliseconds and notifies the kernel via an interrupt only after the 8th transaction completes. (basically I'm making sure I understand the division of labor between hardware and software). On Wed, Jan 2, 2013 at 8:39 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 1 Jan 2013, Shawn Lewis wrote: > >> Sure. These are from playing a 100Hz sine wave tone over the USB sound card. >> >> This is with the wifi device disabled (meaning its not present in >> ifconfig's output, no wifi interrupts occur). No audible pops occurred >> in this sample. >> http://dl.dropbox.com/u/324766/usb-popping/usbmon-100Hz-nowifi.txt >> >> This is with the wifi device enabled (present in ifconfig's output, >> hundreds of wifi interrupts per second) and wifi traffic being >> generated by ping flooding. Audible pops occurred frequently (up to a >> few times per second) in this sample. >> http://dl.dropbox.com/u/324766/usb-popping/usbmon-100Hz-wifi.txt > > The "wifi" usbmon trace doesn't show anything wrong. All the data was > sent to the driver in plenty of time and all the transfers completely > normally, when they were supposed to. Thanks for checking it out. > > Maybe the analyzer trace will be more fruitful. Just because the > driver got its data in time doesn't mean the data appeared on the wire. > You said something about partial packets; what happened there? Here is an audio recording and usb analyzer output. This is a 100hz tone played while wifi traffic is being generated. I've confirmed that errors captured in the analyzer trace correspond to errors in the actual audio recording. I'd seen partial packets before but I don't see them in this trace. http://dl.dropbox.com/u/324766/usb-popping/usb-popping.tgz File descriptions: USB analyzer output in the analyzer's native format. Can be opened with the "Data Center software" program from this page: (http://www.totalphase.com/support/product/beagle_usb480/) 100hz-wifi.tdc USB analyzer output in csv form. (look at the error column to find errors) 100hz-wifi.csv Audio recording in signed 16-bit stereo wav. 100hz-wifi-audio.wav Audio recording in audacity's format: 100hz-wifi-audio.aup Audacity data: 100hz-wifi-audio_data/ > > Also, can you post the portion of /sys/kernel/debug/usb/devices that > describes the sound card? Here's the host controller and sound card. T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 1 B: Alloc= 0/800 us ( 0%), #Int= 0, #Iso= 0 D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=01 MxPS=64 #Cfgs= 1 P: Vendor=1d6b ProdID=0002 Rev= 3.03 S: Manufacturer=Linux 3.3.8 ehci_hcd S: Product=Generic Platform EHCI Controller S: SerialNumber=ehci-platform C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 0mA I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=256ms T: Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 3 Spd=12 MxCh= 0 D: Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 P: Vendor=0d8c ProdID=0139 Rev= 1.00 S: Manufacturer=C-Media Electronics Inc. S: Product=USB PnP Sound Device C:* #Ifs= 4 Cfg#= 1 Atr=80 MxPwr=100mA I:* If#= 0 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=snd-usb-audio I:* If#= 1 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio I: If#= 1 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio E: Ad=01(O) Atr=09(Isoc) MxPS= 200 Ivl=1ms I:* If#= 2 Alt= 0 #EPs= 0 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio I: If#= 2 Alt= 1 #EPs= 1 Cls=01(audio) Sub=02 Prot=00 Driver=snd-usb-audio E: Ad=82(I) Atr=09(Isoc) MxPS= 100 Ivl=1ms I:* If#= 3 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=(none) E: Ad=87(I) Atr=03(Int.) MxPS= 4 Ivl=2ms > > Alan Stern > -- 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
