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
