Problem using multiple USB client devices on dm6446

clints

Hi,

I'm having problem using multiple USB client devices on our dm6446 base system. We have a hub attached to the usb port of the dm6446 and a cellular modem and external gps module attached to the HUB. Both devices are recognize by the system but everytime we try to use one device (gps via usb2serial), we are not able to access the cellular module port.

Is this a limitation on the HW of the dm6446 or this is a USB driver issue and is there a patch available we can use. Below is our configuration.

DM6446 running Linux 2.6.18_pro500 (MontaVista0

LSP_2_00_00_06

MVL5

Thanks for the help!

-clint

over 13 years ago

0 clints over 13 years ago

Prodigy 195 points

Anyone out there that can help me out or point me to the right direction?

0 Prateek Bansal over 13 years ago in reply to clints

TI__Expert 4510 points

Hi,

What are the endpoints used in this configuration and what transfer types these endpoints are set to - bulk, isochronous, interrupt?

Prateek

0 yihe over 13 years ago

TI__Guru 67450 points

Clint,

Could you disable the DMA(using the PIO mode only) to see whether it behaves differently?

Regards

yihe

0 yihe over 13 years ago in reply to yihe

TI__Guru 67450 points

DM6446 has 4 HW Endpoint. USB HUB takes one endpoint, and usb2serial dongle would need one INT and 2 buld endpoints.

So there would be not endpoint available for the modem.

That’s the HW limitation of DM6446

regards,

yihe

0 Bert Q. Vlaanderen over 13 years ago in reply to yihe

Prodigy 40 points

According to my understanding, Linux USB hub software should take care of handling more than one USB device, each having several "endpoints", regardless of the nr of "Endpoints" available in the USB host controller hardware.

0 Ajay over 13 years ago in reply to Bert Q. Vlaanderen

TI__Genius 9460 points

There is indeed a limitation of 4 Rx and 4Tx endpoints.

In this use case,

1Rx (INT IN) endpoint goes to Hub,

2Rx (1 INT + 1 BULK IN) and 1Tx goes to usb-to-serial and

2Rx (1 INT and 1 BULK IN) and 1Tx needed for Modem.

So we are short of 1Rx endpoint. There was a feature in linux driver called “Interrupt endpoint scheduling” using which all INT IN can share one physical endpoint and that can help here.

Ajay

0 Bert Q. Vlaanderen over 13 years ago in reply to Ajay

Prodigy 40 points

We are using Linux kernel 2.6.18. Does this version support Interrupt endpoint scheduling?

In general, isn't an end-point in Linux a virtual port rather than hardware port, and thus there should be no hardware limitation applicable to the number of Linux USB end-points?

Bert.

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Problem using multiple USB client devices on dm6446