Hi Greg, 1. What kernel version are you using here? Sorry about the lack of info. The kernel is: SOCKit: Angstrom v2016.12 - Kernel 4.1.22-ltsi-altera 2. Why is this an "issue"? Is the device not working properly? It is an issue because it makes the CPU busier and when I have another application which needs to run with low latency, these interrupts get in the way because I think they have higher priority. I don't know whose fault it is, hardware, driver or kernel, I just was wondering why it behaves different with the USB hub connected. Regards, Billy. On Wed, Nov 15, 2017 at 1:58 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, Nov 15, 2017 at 12:12:16PM +0000, Billy Araujo wrote: >> Hi all, >> >> I built a kernel/rootfs for altera SoCkit amd uses the default SoCkit >> device tree and I plug when in plug in a USB stick it uses the dwc2 >> driver. > > What kernel version are you using here? > >> When doing cat /proc/interrupts I get normal amount of interrupts - >> everything seems ok. >> >> However, when I connect the USB stick to a USB hub and then to the >> same USB port I get a great amount of interrupts approx. 8000 per >> second. Anyone know why this different behaviour? >> >> root@cyclone5:~# cat /proc/interrupts >> >> CPU0 >> >> 16: 53922 GIC 29 Edge twd >> >> 17: 0 GIC 199 Level timer0 >> >> 18: 0 GIC 136 Level ffe01000.pdma >> >> 26: 0 GIC 190 Level ffc04000.i2c >> >> 27: 0 GIC 191 Level ffc05000.i2c >> >> 29: 24718 GIC 171 Level dw-mci >> >> 40: 1138 GIC 194 Level serial >> >> 41: 3946968 GIC 160 Level ffb40000.usb, ffb40000.usb, >> dwc2_hsotg:usb1 >> >> >> >> root@cyclone5:~# [ 651.854021] usb 1-1: new high-speed USB device >> number 7 using dwc2 >> >> [ 652.065190] usb 1-1: New USB device found, idVendor=05e3, idProduct=0608 >> >> [ 652.071869] usb 1-1: New USB device strings: Mfr=0, Product=1, SerialNumber=0 >> >> [ 652.079007] usb 1-1: Product: USB2.0 Hub >> >> [ 652.088468] hub 1-1:1.0: USB hub found >> >> [ 652.092830] hub 1-1:1.0: 4 ports detected >> >> [ 652.374026] usb 1-1.1: new high-speed USB device number 8 using dwc2 >> >> [ 652.475473] usb 1-1.1: New USB device found, idVendor=05e3, idProduct=0608 >> >> [ 652.482331] usb 1-1.1: New USB device strings: Mfr=0, Product=1, >> SerialNumber=0 >> >> [ 652.489639] usb 1-1.1: Product: USB2.0 Hub >> >> [ 652.499214] hub 1-1.1:1.0: USB hub found >> >> [ 652.503762] hub 1-1.1:1.0: 4 ports detected >> >> >> I have seen several threads with stating this issue but haven't found >> a clear answer. > > Why is this an "issue"? Is the device not working properly? Is the > device not seen correctly? USB is a "constantly asking the device for > data" type of protocol, lots of interrupts is a normal thing. > > Heck, we know of some machines where you plug a USB keyboard into them > and it starts to take 30% of the CPU time up just to handle the > interrupts. That's not USB's fault, or the kernels, it's the horrible > hardware implementation that the board has on it, where it is up to the > CPU to do most of the work. Odds are that is what is happening here > with your platform. > > thanks, > > greg k-h -- 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
