> From: dingu...@opensource.altera.com [mailto:dingu...@opensource.altera.com] > Sent: Monday, September 15, 2014 8:23 AM > > Hi Ming-Lei, > > Thanks for your patch to enable the URB giveback in a tasklet context for > the EHCI driver. I found your patch to fix a USB webcam timeout/stutter > issue on the DWC2 HCD in the SOCFPGA platform. > > However, I need your help trying to figure out why I need the 2nd patch to > get your URB giveback patch to fully work. > > I enable tracepoints in the dwc2 dwc2_handle_hcd_intr for > irq:irq_handler_entry > and irq:irq_handler_exit. However, I did not see any measurable differences > between enabling HCD_BH and no enabling HCD_BH. But I am able to get a full > image from a webcam with the following 2 patches, and timeouts/green screen > without the 2 patches. > > I am using a Logitech HD C270 webcam. > > Opening video decoder: [raw] RAW Uncompressed Video > Movie-Aspect is undefined - no prescaling applied. > VO: [sdl] 640x480 => 640x480 Packed YUY2 > Selected video codec: [rawyuy2] vfm: raw (RAW YUY2) > > Can you provide any comments on the following issues: > > 1) Am I placing the tracepoints in the right place for this non-ehci hcd? > 2) I don't quite understand why removing local_irq_save/local_irq_restore > around the the complete makes the webcam work? > > Thanks in advance for your comments.
Hi Dinh, I'm not Ming, but I can hazard a guess why you are seeing this issue. The webcam driver is likely doing a lot of processing in the ->complete callback. With local interrupts disabled, this probably causes too long of a delay in handling other interrupts. Since the SOCFPGA platform is a uniprocessor (I think), there is no other CPU to handle the other interrupts. I think the only solution is to look at whatever driver is handling the webcam, and see if it can re-enable interrupts earlier. I believe this is an OK thing for it to do when the interrupt handler is threaded. Ah, wait. I just looked at the specs, and I see the SOCFPGA is dual-core. So the second core should be available for handling the other interrupts. I wonder if something is wrong there? Is the 2nd CPU actually running? Are interrupts getting disabled on both CPUs somehow? -- Paul -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
