2016-07-20 9:09 GMT+03:00 Matwey V. Kornilov <matwey@xxxxxxxxxx>: > 2016-07-20 0:34 GMT+03:00 Bin Liu <b-liu@xxxxxx>: >> 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. >> > > Now I see. I've googled it, they start from $1000, I don't know > when/whether/where I can get one to try. > Until that, could I check something else? For instance, disable > CONFIG_USB_TI_CPPI41_DMA. > > I've found that after hours of transmit, the camera stops iso at all > (until reset). Maybe its brain becomes damaged by the transfer issues > at the some moment. > > I've just also made some usbmon records and see that even when there > are no frames in userspace there is iso transfer occuring. > > 160x140: https://yadi.sk/d/BmUCPP_EtT8SN > 640x480 (no frames in user space): https://yadi.sk/d/KXLU-g9-tT8T7 > > Maybe pwc people could give some useful insight looking into the records. > > AFAIU pwc camera support transfer compression and pwc driver > negotiates automaticly the best possible compression level (older > kernal provided module option to do it manually). > However, in pwc_isoc_init(), I see the following > > /* We first try with low compression and then retry with a higher > compression setting if there is not enough bandwidth. */ > ret = pwc_set_video_mode(pdev, pdev->width, pdev->height, pdev->pixfmt, > pdev->vframes, &compression, 1); > > and ret is never checked and is being overwritten a few lines further. > I also have part of dmesg output: https://yadi.sk/d/tjr4EljCtTNbV but not sure that it can help. > > >> 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 >> > > > > -- > With best regards, > Matwey V. Kornilov. > Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia > 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382 -- 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
