logo

Could not compile stylesheet for simplistic. Using last compiled stylesheet.

usb otg speed problem

posted in Linux Kernel
Friday, February 15 2013, 10:14 AM
0
Hi,

I am testing the USB OTG speed and here are the results of hdparm on a USB disk:
-on usb host:
hdparm -t -T /dev/sda
/dev/sda:
 Timing cached reads:   634 MB in  2.00 seconds = 316.60 MB/sec
 Timing buffered disk reads:  72 MB in  3.05 seconds =  23.61 MB/sec

-on usb otg:
hdparm -t -T /dev/sda
/dev/sda:
 Timing cached reads:   404 MB in  2.00 seconds = 201.91 MB/sec
 Timing buffered disk reads:   8 MB in  3.22 seconds =   2.49 MB/sec

In both cases, the drive is plugged to a powered usb hub.

USB host is clearly faster.

I am not sure if it is related (but it must be), if I plug a webcam on the USB OTG port (through a powered hub), I can't get images. The webcam is working well on the USB host port.

I am using kernel 2.6.37-5 from ISEE.

Any ideas?
Thanks for your help.
Regards,
Guillaume

Accepted Answer

Tuesday, February 19 2013, 09:20 AM - #permalink
0
Hi Guillaume,

I got similar results. Please, could you post a bug in:

http://bug.isee.biz

You can create an account if you don't have one.
The reply is currently minimized Show
Responses (1)
  • Accepted Answer

    Monday, February 18 2013, 02:50 PM - #permalink
    0
    Hi,

    As suggested by Enric, I modified my .config with:
    CONFIG_OMAP_32K_TIMER_HZ=1000
    # CONFIG_NO_HZ is not set
    

    The result is a little bit better for usb otg:
    hdparm -t -T /dev/sda
    /dev/sda:
     Timing cached reads:   536 MB in  2.00 seconds = 267.34 MB/sec
     Timing buffered disk reads:  20 MB in  3.26 seconds =   6.14 MB/sec
    


    But it is still far from usb host results. Moreover this does not solve the webcam problem.

    Guillaume
    The reply is currently minimized Show
Your Reply

SUPPORT


This email address is being protected from spambots. You need JavaScript enabled to view it.
This email address is being protected from spambots. You need JavaScript enabled to view it.
IGEP Community Wiki
IGEP Community Forum
IGEP Community Online Chat