Pratik, The increased interrupt activity during ISO transactions is expected. Can you provide information on the actual issue you are facing. Are you not able to stream/run application etc. due to the increased interrupts? Regards Swami > -----Original Message----- > From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb- > owner@xxxxxxxxxxxxxxx] On Behalf Of Pratik Prajapati > Sent: Friday, February 19, 2010 3:06 PM > To: linux-usb@xxxxxxxxxxxxxxx > Subject: need to know about usbaudio. > > Hello, > > I'm doing playback/record with usbaudio on TI musb with ALSA. > > My concern is, in isochronus mode (with CPPI DMA) I see a lot of > interrupts and so ksoftirqd takes up to 30% CPU in addition to Audio > application. And in bulk mode(with CPPI DMA) I see less interrupts and > also ksoftirqd is taking around 15% CPU in addition to the > application. Is there any way by which I can get lesser interrupts in > sochronus mode (with CPPI DMA)? > > my linux is: 2.6.10_mvl401, with > musb_hdrc: version 2.2a/db-0.4.8 [cppi-dma] [host] [debug=1] > musb_hdrc: ConfigData=0x06 (UTMI-8, dyn FIFOs, SoftConn) > musb_hdrc: MHDRC RTL version 1.300 > musb_hdrc: USB Host mode controller at c8002000 using DMA, IRQ 12 > musb_hdrc musb_hdrc: new USB bus registered, assigned bus number 1 > > I have observed that whether I play 8KHZ audio or 44KHZ audio, I see > iso_frame_desc (packed in urb) ramains of same length, i.e. 176 bytes. > e.g. > I played 8KHZ audio and found that, musb is gets total 4 > iso_frame_desc in each URB. size of each iso_frame_desc is 176 bytes. > I played 44KHZ audio and found that, musb is gets total 4 > iso_frame_desc in each URB. size of each iso_frame_desc is 176 bytes. > In each URB musb gets 4 iso_frame_desc, which is fixed by variable > 'static int nrpacks' in usbaudio.c. > > CPPI DMA makes buffer discriptors of each iso_frame_desc, which is > very small chunk. > > Does it make sense that usbaudio passes larger iso_frame_desc to musb > ( right now I'm getting 176 bytes iso_frame_desc each time)? so that > CPPI DMA will send lesser interrupts to CPU. > > Please let me know if more information is required from my side. > > -- > Regards, > Pratik PRAJAPATI > -- > 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 -- 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
