It seems that the ultimate cause for all this strangeness was a mis-wired board: the vendor at long last admitted that the VBUS signal is not connected in the hardware. Why they didn't simply document this fact, and thereby save me a lot of wasted effort, remains a mystery.This reserved bit seems to be an alias to the earlier mentioned PUEN bit
As a workaround, they suggested setting bit 0x00000010 in the ctl register, which is strangely enough inside the "reserved" space according to the AMD data book. Worth a shot, I thought. After hacking up the amd5536udc driver even more to do this operation at load time, the register states change to:
cap=0x000083EA
mux=0x00000007
ctl=0x00000193
Seems that a few other "reserved" bits also raised in response. (I still do not understand exactly how they wired up the CS5536 IO chip to be different from the data book, but oh well.) In this mode, the USB link is finally detected, and the board is finally able to enumerate itself as a g_zero device.
Please accept my sincere thank-you for your help. I'm hoping that everything will work from now on, and that I won't send any more questions your way. :)My pleasure! It is fun for me to continue this thread.
I'll also await an update to the irq stuff in the amd5536udc driver that we talked about earlier, if you get around to making the fix for it first.I will do when I have a new CS5536 board. Thanks for your