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DM6446: problems with more than USB devices

H. Dengler
Prodigy 10 points
Hi,

we've some troubles with DM6446 and the USB-controller. Our custom-hardware is based on a DM6446ZWT and connected to this is a hard-wired 7-port USB Hub. The USB Controller is configured as host. We're currently using kernel 2.6.32.17

If we connect more devices to the hub, we're getting some problems. The probelms seams appear only with Endpoints of type INTERRUPT (direction IN). Device with in summary up to 2 endpoints are ok, but starting with the 3rd, we're getting reset messages for this one. (if there are no devices pluged into the hub, lsusb shows 2 EPs in/interrupt, I guess one for the internal hub and one for the 7-port hub on the board).

I know, that there is a limitation in the controller to 4(+1) EPs (each RX and TX). And I also know, that in kernel 2.6.32 there is a config option to schedule the interrupt EPs. Unfortunately this option generates other problems, therfore I have some questions about all this.

1) If I enable CONFIG_MUSB_SCHEDULE_INTR_EP the reset messages are gone, but we're getting lots of interrupt (without any actions on the devices e.g. pressed keys on the keyboard). Is this a known issue? How can I get it top work properly?

2) I checked newer kernels for the CONFIG_MUSB_SCHEDULE_INTR_EP option, but it seams to me, that it no longer exist. Is this option now permanently integrated in the musb device driver? If the anser is yes, how many devices support newer kernels (e.g. 3.0 and higher)?

3) Why do our troubles start with the 5th EP in/intr (1x EP internal hub, 1x EP external hub, 3x device EPs), if the cotroller is (theoretically) limited to 4+1 EPs?

4) A more general question: If the number of EP is limited to 4 EPs (RX/TX), why do we get these reset messages, if we add a device with an interrupt EP, but adding several devices with bulk EPs seams to work without any problem?

PS: I already searched for help here in the forum, but unfortunately I didn't find a solution for my problems yet. If there are already topics for one or more of my questions, I also appreciate if you can give me a link.

Thanks and many greetings,
H. Dengler