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.
Thanks for your help.
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.