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 <gre...@linuxfoundation.org> wrote:
> On Wed, Nov 15, 2017 at 12:12:16PM +, 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 ffb4.usb, ffb4.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
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