Hello, We are attempting to create a system that will support 8 full speed USB devices each sending a 64-byte transfer every 1ms via interrupt endpoints. When we connect 5 full speed USB devices our USB host use 24% of the CPU, but when we connect a 6th device, the CPU goes to 100%. Has anyone else seen this type of CPU jump or know what could be causing it?
Devices CPU Total Throughput 1 7% 64 KB/s 2 11% 128 KB/s 3 15% 192 KB/s 4 19% 256 KB/s 5 24% 320 KB/s 6 99% (should be 384 KB/s, but the iMX535 misses sending IN tokens in some SOF periods) We are using a Freescale iMX535 board running at 800 MHz as the USB host. One of the iMX535 EHCI root controllers is connected to a high speed USB hub which has two ports each connected to another high speed USB hub (giving us 8 ports for USB devices). Each hub has multi-TT support. The iMX535 is running Linux 2.6.35, and our test application uses libUSB asynchronous I/O (v1.0.16). The libUSB callback function do not process the data; rather the function only resubmits the transfer. We only have the EHCI driver enabled. CONFIG_USB_EHCI_ROOT_HUB_TT=y CONFIG_USB_EHCI_TT_NEWSCHED=y # CONFIG_USB_ARCH_HAS_OHCI is not set Thanks for the help. -Nate -- 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
