USB Issue Troubleshooting

Hi all,
There are quite a few posts related to USB port failures. The goal of this post is to summarize all of them and to set the record straight.
The issue:
The USB phy does not always get initialized properly coming out of reset on some boards. After successful initialization, the USB port works fine.
Statements:
*Since day one, we have tested the USB port on every board shipped
*We have shipped 10,000 Parallella boards to 7,000 customers to date and have only received issue reports from a small number of customers
*We have spent significant time debugging this problem (internal to Adapteva and external) and unfortunately we have not found an acceptable bullet proof workaround yet
*We will keep working on resolving this issue, but given our limited resources and other high priority items that need to be dealt with, we can't give a time line for when this will be resolved.
Some data:
* The probability of successful USB initialization varies between boards.
* Keeping USB device plugged in during powerup increases probability of success
* A power cycle reset is more likely to work than a push button reset
* Probability of success increased by using longer USB cables
* Probability of success increased by using certain USB peripherals/hub setups
* Most boards work with all combination of hubs/peripherals (no restrictions)
How to report a USB problem:
* Failure mode (sometimes or always?)
* Headless/hdmi configuration
* FPGA/Linux/Ubuntu version being used
* Fan used?
* SKU#
* For SKU A101040 boards owners, an indication whether the U13 device is populated
* Power supply used
* Recommended: A picture of your USB setup (as shown here)
Sincerely,
Andreas
There are quite a few posts related to USB port failures. The goal of this post is to summarize all of them and to set the record straight.
The issue:
The USB phy does not always get initialized properly coming out of reset on some boards. After successful initialization, the USB port works fine.
Statements:
*Since day one, we have tested the USB port on every board shipped
*We have shipped 10,000 Parallella boards to 7,000 customers to date and have only received issue reports from a small number of customers
*We have spent significant time debugging this problem (internal to Adapteva and external) and unfortunately we have not found an acceptable bullet proof workaround yet
*We will keep working on resolving this issue, but given our limited resources and other high priority items that need to be dealt with, we can't give a time line for when this will be resolved.
Some data:
* The probability of successful USB initialization varies between boards.
* Keeping USB device plugged in during powerup increases probability of success
* A power cycle reset is more likely to work than a push button reset
* Probability of success increased by using longer USB cables
* Probability of success increased by using certain USB peripherals/hub setups
* Most boards work with all combination of hubs/peripherals (no restrictions)
How to report a USB problem:
* Failure mode (sometimes or always?)
* Headless/hdmi configuration
* FPGA/Linux/Ubuntu version being used
* Fan used?
* SKU#
* For SKU A101040 boards owners, an indication whether the U13 device is populated
* Power supply used
* Recommended: A picture of your USB setup (as shown here)
Sincerely,
Andreas