WLAN device disappears permanently

[wad]

We have been having a significant number of motherboards in the field which stop communicating with their WLAN module. These all worked fine, sometimes for months, then suddenly refused to find the WLAN module when enumerating the USB bus. Once this occurs, the device does not reappear, even after power-cycles, full system reset, etc.

These are production (C2) laptops. It is unknown if it also happened on earlier motherboards.

This is confirmed to occur on all laptop builds between 656 and 703. It might also be happening on earlier and later builds.

I started diagnosing one of these laptops by disconnecting the USB connection between the Southbridge and the WLAN module, attaching a USB cable to the module, and testing if it would work on another USB port (or even another laptop). The device was still not found.

I quickly checked that the WLAN processor was running -- operating voltages were fine and I could see it fetching data from it's serial flash.

Next, I swapped the serial flash with a serial flash from a working machine. This corrected the problem !

I read the data off the flash device that wasn't working -- it is attached to this ticket.

There is a slight possibility that it was the heating of the WLAN module to remove the serial flash that corrected the problem, and not the actual change of flash.

[wad]

Serial flash image (in binary format) from a non-functional WLAN interface

[wad]

I was just informed that the unit I replaced the WLAN flash on had actually been intermittent. Countries are sending me more broken units to test.

[gregorio]

Hi Wad,

Is this a hardware or SW problem?

Just trying to understand if I need to track in under releases.

Thanks,

Greg S

[wad]

Is firmware software ?

This is most likely to either be a manufacturing issue or a WLAN firmware issue.

[mstone-xmlrpc]

Pushing out to 9.1.0, per edmcnierney's request.