Hi, On Wed, Jul 20, 2016 at 12:25:44AM +0300, Matwey V. Kornilov wrote: > 2016-07-19 23:56 GMT+03:00 Bin Liu <b-liu@xxxxxx>: > > Hi, > > > > On Tue, Jul 19, 2016 at 11:21:17PM +0300, matwey@xxxxxxxxxx wrote: > >> Hello, > >> > >> I have Philips SPC 900 camera (0471:0329) connected to my AM335x based BeagleBoneBlack SBC. > >> I am sure that both of them are fine and work properly. > >> I am running Linux 4.6.4 (my kernel config is available at https://clck.ru/A2kQs ) and I've just discovered, that there is an issue with frame transfer when high resolution formats are used. > >> > >> The issue is the following. I use simple v4l2 example tool (taken from API docs), which source code is available at http://pastebin.com/grcNXxfe > >> > >> When I use (see line 488) 640x480 frames > >> > >> fmt.fmt.pix.width = 640; > >> fmt.fmt.pix.height = 480; > >> > >> then I get "select timeout" and don't get any frames. > >> > >> When I use 320x240 frames > >> > >> fmt.fmt.pix.width = 320; > >> fmt.fmt.pix.height = 240; > >> > >> then about 60% frames are missed. An example outpout of ./a.out -f is available at https://yadi.sk/d/aRka8xWPtSc4y > >> It looks like there are pauses between bulks of frames (frame counter and timestamp as returned from v4l2 API): > >> > >> 3 3705.142553 > >> 8 3705.342533 > >> 13 3705.542517 > >> 110 3708.776208 > >> 115 3708.976190 > >> 120 3709.176169 > >> 125 3709.376152 > >> 130 3709.576144 > >> 226 3712.807848 > >> > >> When I use tiny 160x120 frames > >> > >> fmt.fmt.pix.width = 160; > >> fmt.fmt.pix.height = 120; > >> > >> then more frames are received. See output example at https://yadi.sk/d/DedBmH6ftSc9t > >> That is why I thought that everything was fine in May when used tiny xawtv window to check kernel OOPS presence (see http://www.spinics.net/lists/linux-usb/msg141188.html for reference) > >> > >> Even more. When I introduce USB hub between the host and the webcam, I can not receive even any 320x240 frames. > >> > >> I've managed to use ftrace to see what is going on when no frames are received. > >> I've found that pwc_isoc_handler is called frequently as the following: > >> > >> 0) | pwc_isoc_handler [pwc]() { > >> 0) | usb_submit_urb [usbcore]() { > >> 0) | usb_submit_urb.part.3 [usbcore]() { > >> 0) | usb_hcd_submit_urb [usbcore]() { > >> 0) 0.834 us | usb_get_urb [usbcore](); > >> 0) | musb_map_urb_for_dma [musb_hdrc]() { > >> 0) 0.792 us | usb_hcd_map_urb_for_dma [usbcore](); > >> 0) 5.750 us | } > >> 0) | musb_urb_enqueue [musb_hdrc]() { > >> 0) 0.750 us | _raw_spin_lock_irqsave(); > >> 0) | usb_hcd_link_urb_to_ep [usbcore]() { > >> 0) 0.792 us | _raw_spin_lock(); > >> 0) 0.791 us | _raw_spin_unlock(); > >> 0) + 10.500 us | } > >> 0) 0.791 us | _raw_spin_unlock_irqrestore(); > >> 0) + 25.375 us | } > >> 0) + 45.208 us | } > >> 0) + 51.042 us | } > >> 0) + 56.084 us | } > >> 0) + 61.292 us | } > >> > >> However, pwc_isoc_handler never calls vb2_buffer_done() that is why I get "select timeout" in userspace. > >> Unfortunately, my kernel is not compiled with CONFIG_USB_PWC_DEBUG=y but I can recompile it, if you think that it could provide more information. I am also ready to perform additional tests (use usbmon maybe?). > >> > >> How could this issue be resolved? > >> > >> Thank you. > > > > Do you have CPPI DMA enabled? If so I think you might hit on a known > > issue in CPPI Isoch transfer, in which the MUSB controller only sends IN > > tokens in every other SOF, so only half of the bus bandwidth is > > utilized, which causes video frame drops in higher resolution. > > > > Yes, I do use DMA: > > CONFIG_USB_TI_CPPI41_DMA=y Okay. > > > To confirm this, use a bus analyzer to capture a bus trace, you would > > see no IN tokens in every other SOF while transfering Isoch packets. > > > > I am sorry, I am new to USB debugging. Do you mean I need to use > usbmon or some external hardware device? I barely use usbmon, and not sure if it gives the information I am looking for. But I meant the external test equipment - USB bus protocol analyzer - a bus packet sniffer. Regards, -Bin, > > > Regards, > > -Bin. > > > > > > -- > With best regards, > Matwey V. Kornilov. > Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia > 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
